High-resolution imaging of the structural changes to Pt-based catalyst nanoparticles supported on carbon blacks using in-situ electrochemical liquid cell transmission electron microscopy (TEM) are being correlated with the behavior of similar materials incorporated in membrane electrode assemblies (MEAs) subjected to accelerated stress tests (ASTs), to elucidate catalyst and catalyst-support degradation phenomena contributing to fuel cell performance loss. Specialized in-situ holders for the TEM have been developed that enable the interactions between catalyst particles and their supports to be imaged during potential cycling in relevant liquid electrolytes, such that the critical stages of materials corrosion during fuel cell operation can be imaged in real time at nm-scale resolution. The direct TEM observations of the changes to the catalyst (Pt dissolution and particle growth/coalescence) and carbon supports (mechanisms of progressive support corrosion) during in-situ electrochemistry, combined with the post-mortem evaluation of cathode layers comprised of similar Pt/C materials after AST of MEAs, provide an unprecedented means by which to “capture” catalyst and catalyst-support degradation mechanisms such that materials optimization strategies can be implemented to enhance fuel cell durability.
Research sponsored by (1) the Office of Fuel Cells Technologies, Office of Energy Efficiency and Renewable Energy, the U.S. Department of Energy and (2) ORNL&’s Center for Nanophase Materials Sciences, Scientific User Facilities Division, Office of Basic Energy Sciences, the U.S. Department of Energy.

Fuel cells based on polymer electrolyte membranes (PEM) show promise as a means of energy conversion for a wide range of applications both in the transportation sector and for stationary power production due to their high charge density and low operating temperatures. Devices are assembled with multiple heterogeneous materials and failure, or performance losses, can largely occur at the interfaces between these materials. While the structure and transport of bulk PEMs for fuel cell applications have been studied extensively, there has been little effort focused on these materials at interfaces and under confinement as they exist within the membrane electrode assembly (MEA) of a working PEM fuel cell. Using a combination of neutron and x-ray reflectivity, grazing-incidence small-angle x-ray scattering (GISAXS), quartz crystal microbalance (QCM), as well as polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS) we have studied the polymer-substrate interfacial structure, thin film nano-scale structure, the swelling, and water transport behavior as a function of humidity, surface chemistry, and initial film thickness (< 220 nm). We have found the interfacial structure to be highly dependent upon the substrate surface chemistry. Moreover, when the polyelectrolyte is confined to thin films there is suppression in both swelling and water diffusivity. Specifically, we observe that the relative humidity-dependent, equilibrium swelling ratio and volumetric water fraction is constant for films above 100 nm. A clear transition in the swelling response, absorbed water content, and the diffusivity (as determined from the time-dependent PM-IRRAS signal) is observed for films thinner than 60 nm. More recently, we have used a technique developed at NIST to measure the mechanical properties of these systems. Preliminary results reveal that confinement also plays a significant role in the mechanical response of Nafion and may help in elucidating the molecular origins for the observed changes in water uptake and transport. It is speculated that these confinement affects should also have an impact on the proton conductivity and overall fuel cell performance. Our studies clearly show that the behavior of the materials under confinement can be quite different than in the bulk. Current fuel cell modeling efforts rely on bulk property values, when considering the catalyst layers and interfaces, to predict structure, transport and fuel cell performance. With this new information, researchers will be able to more accurately model the performance of the MEA within a working fuel cell which could lead to improvements in MEA design and more efficient operating conditions.

One of the major issues affecting the durability of PEMFC (Proton Exchange Membrane Fuel Cells) is electrode degradation over time. Indeed, in fuel cell conditions conventional electrocatalyst supports based on carbon suffer from corrosion leading to detachment and migration, or aggregation of electrocatalyst nanoparticles, and loss of performance. One strategy to overcome this issue is the replacement of carbon with (electro)chemically more stable supports. We are currently developing novel nanofibre and nanospherical based PEMFC support materials using alternative materials, including doped oxides and semi-conducting carbides. The challenges to be addressed are related to the development of non-carbon support materials having sufficient surface area to well disperse the electrocatalyst nanoparticles, while ensuring adequate electronic conductivity. We will review current progress in this area, and focus on morphology and physical-chemical properties of non-carbon supports prepared by electrospinning and hydrothermal methods, and the challenges of electrode development from them. Electrocatalytic activity of these systems will be addressed, in particular towards the oxygen reduction reaction, and the results of testing under accelerated ageing protocols will be described in order to compare their resistance to corrosion to that exhibited by conventional carbon based supports and assess their greater stability, and to underline the importance of a strong catalyst support interaction.

Development and optimization of electrocatalysts, supports and components for fuel cells are hindered by the complex nature of the materials, a partial understanding of the reaction mechanisms and precise chemistry of the active site or sites and relationship between performance and morphological properties such as size of particles, surface area, roughness, porosity, etc.
XPS is one of the most widely utilized surface spectroscopic techniques for the analysis of catalyst structure. XPS is widely applied to supported nanostructured catalysts because it allows discriminating between oxidation states of the metal, including unusual ones which may play a key role in catalyst behavior.
Surface morphology is one of the most important factors affecting functional performance of components. Digital image processing (DIP) of SEM images is able to convert the 2-D intensity distribution into 1-D image descriptors that are utilized for quantitative morphology analysis. Different phenomena and processes related to the material performance correspond to different diffusion regimes at different lengthscales. A vitally important for functional characterization must be an appropriate separation of the different components of surfaces, which is not only to extract roughness, waviness and form, but also should be extended to concern all multi-scalar topographical events over surface.
Predicting macroscopic properties of interest, such as catalytic activity and stability, from materials chemistry and structure is challenging yet feasible using a multianalytical approach combined with multivariate analysis. Correlation of structure, morphology and performance of different families of materials relevant for energy applications is achieved through the application of principal component analysis (PCA).
This talk will discuss structure-to-property correlations for two different systems. The first material set are a non-platinum Group Metal (Non-PGM) ORR electrocatalysts. Due to the heterogeneous nature of the materials the basic understanding of the interplay between chemistry and morphology of the active sites is missing. The correlation between chemical composition and environment and pore size is critical in understanding catalytic performance.
In the second problem we will address durability of the catalyst layer (CL) which is linked to catalyst dissolution and agglomeration, ionomer degradation, carbon support degradation, and the degradation of pore morphology and surface properties. It is essential to determine parameters representing composition, structure and properties of cathode components and catalysts layer for the optimization of performance and durability.

Despite efforts to eliminate platinum-group metals (PGM) from fuel cell electrodes, the noble metals remain the most active and durable materials currently available. The current frontiers of PGM catalyst research include the synthesis of nanostructured alloys and extended metallic surfaces with extremely high activity for the oxygen reduction reaction (ORR).
While electrochemical and physical vapor deposition routes have demonstrated unique capabilities in the synthesis of supported and unsupported advanced PGM catalysts, chemical vapor deposition (CVD) methods have comparatively been overlooked. Conventional CVD is routinely applied to the fabrication of complex, functional planar nanostructures, but it is often unsuited for film deposition on powders and fibers, or within high aspect-ratio microstructures. Increasing interest in these substrates for electrocatalysis and energy conversion applications has provided considerable impetus to devise new deposition routes.
We have developed a simple, inexpensive, CVD-like fixed-bed approach to the deposition of PGM nanoparticle dispersions on finely divided substrates using metalorganic precursors. This process requires no specialized apparatus, and is conducted at mild temperatures (150 C - 270 C). During the deposition process, substrate surface chemistry initiates precursor decomposition and deposition of nanoparticle networks composed of constituent particles as small as 2 nm.
Conformal coatings with extremely high aspect ratios can also be produced within porous monolithic substrates. Subsequent thermal treatments induce morphological evolution of the deposited networks, including alloying and the development of nanoscale porosity. Sacrificial porous templates can be dissolved, liberating unsupported nanostructured catalysts. Porous Pt nanotubes produced via this method showed a specific activity for the ORR of 2400 uA cm-2 at 0.9 V. Additional case studies from low- and intermediate temperature technologies will be shown to illustrate the power and versatility of the technique for PGM catalyst synthesis.

Developing new synthetic methods for the controlled synthesis of Pt-based or non-Pt nanocatalysts with low or no Pt loading to facilitate sluggish cathodic oxygen reduction reaction (ORR) and organics oxidation reactions is a key issue in the development of fuel cell technology. Various nanoparticles (NPs), ranging from the size to shape, composition and structure, have shown the good potential to catalyze the sluggish cathodic and anodic reactions. In this presentation, I will talk about my recent advances on synthesis of graphene-FePt, graphene-Co/CoO and graphene-PtPd nanoparticles for effectively enhancing ORR and methanol oxidation reaction.

The ability to engineer transport of mass, heat, and charge in electrochemical power conversion and storage systems such as fuel cells and batteries is critical to ensure optimal operational stability, durability, and performance. I this talk, I will discuss two types of systems, a low temperature polymer electrolyte fuel cell and a vanadium redox flow battery. A combination of computational and experimental approaches will be shown which help us to understand and optimize system performance and durability through enhanced transport. Both systems have complex transport issues which, when engineered through materials, cell architecture or other methodologies, can be optimized.
I the first part of the talk, I will discuss the redox flow battery system as a potential disruptive technology for grid-level energy storage. Work at the University of Tennessee and Oak Ridge National Lab has recently shown an increase in the operating current density of over an order of magnitude compared to conventional systems, while maintaining high efficiency. This achievement enables a tremendous reduction in cost of the power plant. In the second part of the talk, I will discuss our efforts to maximize performance and durability in polymer electrolyte fuel cells. With a non-conventional architecture, we have shown a tremendous reduction in mass transport losses that allow us to push beyond 2 A/cm2 at high voltage. In this high performance system, dry out of the anode is the limiting behavior. Thus, there is a desire to control the direction and magnitude of the net water flux across the fuel cell. This part of the talk will explore the limits of what can be accomplished through engineering of materials within a realistic range of achievable transport parameters. The engineering of thermal and mass transport across the fuel cell will be shown to be capable of reversing the net flux of water as needed for the particular system, without resulting in a trade-off in performance.

The aqueous hydrogen bromide/bromine - hydrogen flow cell under development at Berkeley Lab provides high power density and stable long-term cycling. Peak power of 1.4W/cm2 and >90% efficiency while cycling at 0.4W/cm2 were reported previously. The present work describes efforts to optimize the cell materials and understand degradation mechanisms.
During discharge, a solution of Br2 in HBr (aq) is fed to the cathode compartment where bromine reacts with protons supplied from the anode side and is reduced to bromide, generating the theoretical open circuit potential of 1.098 V at 25°C. On charge, H2 and Br2 are generated from HBr at the (-) and (+) electrodes, respectively. The challenges of this system include: high vapor pressure of bromine gas; migration of water and bromine species to the hydrogen anode, especially during charging; poisoning of the anode Pt catalyst by bromine species; and, formation of mixed aqueous and liquid bromine phases at high states of charge.
Cell materials selection has a large impact on cell performance. We present results for various carbon cathode electrode morphologies, membrane types, and anode catalyst compositions. The relevant materials properties for the carbon cathode are: porosity, tortuosity, effective conductivity, and carbon type. The relevant materials properties for membranes are: proton conductivity, hydrogen permeability, bromine uptake, and electro-osmotic drag coefficient. Long-term cycling results will be discussed in terms of various classes of degradation mechanisms related to: cell materials; crossover of water and electro-active species; and, changes in solution chemistry.

Redox flow batteries (RFB) are considered potential candidates for grid-integrated storage of energy generated by wind, solar and other sustainable resource. However, adoption of RFBs for this application is contingent upon reducing overall system cost. In the well-known case of the aqueous all-vanadium RFB (VRFB), both the energy storage medium and the energy conversion cells contribute significantly to the system cost. One key route to cost reduction of the cells is an increase of cell current density at the desired operating voltage, permitting decreased cell and/or stack size.
To further improve the performance, one must identify and quantify the rate-limiting processes which control the losses in the cell. In previous work, we demonstrated that the voltage losses originating from charge transfer and ohmic processes at various discharge currents can be quantified using electrochemical impedance spectroscopy (EIS) under an idealized condition; and these losses were dominant at the negative electrode.
In this work, we again apply EIS to probe the voltage losses at the VRFB negative electrode. The overvoltages resulting from ohmic, charge transfer and diffusion process are quantified individually at various operating current densities during charge and discharge. More specifically, we will demonstrate and discuss the influences of flow rate and electrode thickness on each overvoltage. The obtained results will be presented to identify and quantify the rate limiting processes at various charge/discharge currents and cell configurations leading to a pathway for performance optimization.

Li-O2 batteries have received considerable attention due to their high specific energy. Several challenges need to be overcome to enable practical applications of Li-O2 batteries, including low round-trip efficiency associated with high overpotentials on charge, electrode and electrolyte instability, and low rate capability at the cathode. Concerted efforts have been directed towards finding successful combinations of electrolyte solvent and cathode material. Recent work showed a 95% capacity retention after 100 cycles by nanoporous gold cathode in dimethyl sulfoxide (DMSO) [1].
We describe the fabrication and implementation of 3-dimensional Au micro-lattices with a relative density of 0.2% into Li-O2 batteries . The lattices were fabricated by first sputtering 500 nm of Au at room temperature onto polymer templates that were formed by self-propagating photopolymer waveguide prototyping at Hughes Research Labs, followed by fully removing the sacrificial polymer scaffold. The relatively non-smooth surface of nanocrystalline Au film in concert with a periodic, hierarchical micro-truss geometry that spans three orders of magnitude in length scale - nm, um, and mm - offers adjustable specific surface area, pore size, and mechanical stability. Surfaces of discharged cathodes are analyzed using SEM, XRD and FTIR, and deterioration is described in the framework of lithium peroxide-forming reactions under different discharge conditions.

[1] Peng et al, Science 2012

High-temperature proton exchange membrane fuel cells (HT-PEMFCs) are an innovative family of highly efficient and environmentally-friendly energy conversion devices typically operating in the range 150HT-PEMFCs use as the electrolyte a polymeric membrane characterized by a high thermal and chemical stability (e.g., polybenzimidazole, PBI). The latter is swollen with a suitable proton-conducting medium, usually H₃PO₄. The resulting system is capable of efficient proton transport in the typical operating conditions of HT-PEMFCs. In this work, innovative hybrid inorganic-organic membranes for application in HT-PEMFCs are developed. The membranes consist of PBI including between 0 and 35 wt% of nanometric HfO₂ and are obtained by solvent-casting processes. HfO₂, which is an interesting nanofiller for its remarkable chemical and electrochemical stability and for the basic character of its surface, plays a crucial role in the development of interactions with the other components of the hybrid membranes (i.e., PBI and H₃PO₄), thus leading to an improved thermal stability and proton conductivity.
The essay of Hf in the hybrid membranes is determined by ICP-AES. The thermal stability and transitions of materials are investigated by HR-TG and DSC measurements, respectively. FT-MIR ATR vibrational spectroscopy measurements carried out on both sides of the membranes allows us to study the structure and interactions in nanocomposite membranes. Finally, the electric response of membranes is measured by broadband electrical spectroscopy (BES) in the 5-190°C and 1-10⁷ Hz temperature and frequency range, respectively. Materials are investigated in completely dry and H₃PO₄-doped state.
In summary, the insertion of HfO₂ nanofiller in bulk hybrid PBI-based materials: a) improves the thermal stability of hybrid membranes: b) inhibits the condensation at high temperature of H₃PO₄ to form H₄P₂O₇; and c) increases the electrical conductivity by a factor of ca. 1.5-2, (a value of 6.6x10^-2 S/cm for the membrane with 11 wt% of the nanofiller is obtained). These features make the proposed hybrid membranes very promising candidates for application in HT-PEMFCs.

Phosphoric acid doped polybenzimidazole (PBI) is the most common membrane material for high-temperature polymer electrolyte fuel cells (HT-PEMFC). The PBI membrane was doped by immersion in hot phosphoric acid. The sojourn time in the acid defines the doping level of the membrane. Despite the fact that this is a standard method to prepare HT-PEMFC membranes, in-depth studies of the morphology of such acid doped PBI membranes are still lacking. In particular, the impact of the doping level on the morphology and its influence on the proton conductivity is not yet well understood. Therefore, we measured the proton conductivity in a full cell setup and employed confocal Raman microscopy to spatially resolve the acid distribution within poly (2, 5-benzimidazole) (AB-PBI) membranes. To our knowledge, this is the first time such experiments are carried out on PBI type membranes.
The proton conductivity improved significantly for membranes with 6 hours of doping time compared with those doped for only 3 hours. However, a merely slight acid up-take occurred. This result shows that the doping level is not the only parameter that defines the conductivity of the membrane. The conductivity is also influenced by the micro acid distribution within the membrane, which can be determined by confocal Raman microscopy. The interactions between the basic N-sites of the AB-PBI polymer and the phosphoric acid were investigated with this method. With increasing doping time a more homogenous distribution of phosphoric acid in the AB-PBI host was observed, indicating stronger interactions between the dopant and the host. Confocal Raman microscopy allows us to study the correlation between the morphology and conductivity of phosphoric acid doped AB-PBI membranes.

Polymer electrolyte membranes (PEMs) are one of the key components in polymer electrolyte membrane fuel cells (PEFCs). It is well known that proton conduction in PEMs causes co-transport of water molecules, whose phenomenon is called by the term “electro-osmosis”. Electro-osmosis leads to the localization of water molecules in the vicinity of the cathode, which reduces the performance of fuel cells. To minimize electro-osmotic drag coefficients (the number of water molecules cotransported with proton conduction), atomistic level understanding on electro-osmosis is necessary. In this presentation, we report results of first-principles molecular dynamics simulations carried out to investigate proton transport and its couplled water transport in PEMs.

The electrochemical performance of solid oxide fuel cells (SOFC) electrodes is strongly influenced by their microstructure [1]. Non-destructive X-ray tomography is a key technique for studying fuel cell electrodes as two dimensional imaging does not capture the full complexity of the microstructures involved [2]. Previously, these SOFCs have been difficult to study in-operando due to the geometry of the devices, as well as the temperature and gas sealing requirements. In this work we present a novel experimental design that allows both X-ray tomography and diffraction to be performed on an operating fuel cell. When coupled with electrochemical techniques, this approach allows for the relationship between operating conditions and microstructural evolution to be better understood.
The fuel cells were found to have an engineered hierarchical pore structure on the anode side. The tortuosity factors of this material were quantified using a simulated diffusion approach [3], which had to be modified for the specific cell geometry considered. This parameter, along with several others, including the specific surface area, could potentially be used in an Adler, Lane and Steele [4] type model, enabling the electrochemical performance of the cell to be predicted and compared with the experimental data obtained.
[1] P.R. Shearing, D.J.L. Brett, N.P. Brandon, Int Mater Rev, 55 (2010) 347-363.
[2] P.R. Shearing, J. Gelb, N.P. Brandon, J Eur Ceram Soc, 30 (2010) 1809-1814.
[3] S.J. Cooper, D.S. Eastwood, J. Gelb, G. Damblanc, D.J.L. Brett, R.S. Bradley, P.J. Withers, P.D. Lee, A.J. Marquis, N.P. Brandon, P.R. Shearing, J Power Sources, (2013).
[4] S.B. Adler, J.A. Lane, B.C.H. Steele, J Electrochem Soc, 143 (1996) 3554.

Various Pt-based metal nanoparticles (NPs) have shown the great potential to catalyze the fuel cell reactions. However, the main problem of these NPs for fuel cells is their limited durability. In this presentation, we focus on our recent advances in rational design and controlled synthesis of FePt-based nanowire (NW) electrocatalysts towards oxygen reduction and methanol oxidation reactions. FePt NWs have been synthesized in high yield via a simple organic phase decomposition of Fe(CO)5 and reduction of Pt(acac)2 in the 1-octadecene and oleylamine solution containing sodium oleate. Treated with acetic acid, these FePt NWs become active and stable for ORR. Through coating FePtPd NWs with 0.8 nm FePt shell, we further found that FePtPd/FePt core/shell NWs are more active and stable for ORR than FePt NWs. Furthermore, we will also show that FePtPd trimetallic NWs are active and durable for MOR.

Supportless one-dimensional (1-D) intermetallic Pt-based nanotubes are considered as promising candidates for the active and durable cathode catalyst in proton exchange membrane fuel cells (PEMFCs). However, one-dimensional Pt-based nanotubes are difficult to produce at large scale because they have generally been synthesized using a template method that requires a multistep synthetic routes. Herein, we report the simple and scalable method to produce intermetallic FePt nanotubes by electrospinning. Collapse of the tubular nanostructure was prevented by in-situ generated silica template during the high temperature heat treatment required for the conversion to fct-FePt intermetallic phase. When tested as cathode catalysts, the resulting material showed 2.2 times higher specific ORR activity than Pt/C. Moreover, a single cell test of the resulting material showed comparable initial performance and superior durability compared to Pt/C. After accelerated durability test by operating at a potential of 1.4 V for 3 h, the maximum power density of membrane-electrode-assembly (MEA) with intermetallic FePt nanotubes decreased only by 8 % whereas that of MEA with Pt/C decreased by 79 %. This approach can be applied to produce a wide range of 1-D tubular intermetallic catalysts with good scalability, tailored composition, and durability at inexpensive cost.

LaMnO₃ is an inexpensive alternative to precious metals (e.g. platinum) as a catalyst for the oxygen reduction reaction in alkaline fuel cells. In fact, recent studies have shown that among a range of non-noble metal catalysts, LaMnO₃ provides the highest catalytic activity. Despite this, very little is known about LaMnO₃ in the alkaline fuel cells environment, where the orthorhombic structure is most stable. In order to understand the reactivity of orthorhombic LaMnO₃ we must first understand the nature of the adsorbate-substrate interactions at the surface. Hence, we have carried out calculations of O₂ adsorption on its electrostatically stable low index surfaces using hybrid-exchange density functional theory, as implemented in CRYSTAL09. The adsorption modes of O₂ on the (100), (001), (101) and (110) surfaces are presented and discussed in terms of their structure and energetics. The reactivity of the adsorption sites that exist on these surfaces towards the oxygen reduction reaction is predicted according to the binding energy and charge transfer to O₂.

Carbon supported cobalt selenides (CoSe2/C) were prepared by a simple microwave method using cobalt acetate and selenium dioxide as precursors with different Se/Co molar ratios. The electrocatalytic activities of CoSe2/C toward oxygen reduction reaction (ORR) were examined by rotating disk electrode (RDE) technique. The effects of Se/Co ratios on surface morphology, crystal structure, chemical composition and ORR activity of catalyst nanoparticles were systematically studied. The experimental compositions of CoSe1.8-CoSe2.7/C with average particle sized 12.4-15.9 nm, major orthorhombic CoSe2 and minor cubic CoSe2 phases could be obtained with the Se/Co ratios of 2.0-4.0. The potentials corresponding to ORR (EORR) reached 0.6-0.7 V, while the electron transfer numbers (n) 3.1-4.0. The Se-rich CoSe2/C prepared with the optimized Se/Co=3.0 exhibited the best ORR activity with the EORR=0.705 V and n=4. It was demonstrated that excess selenium oxide would prevent CoSe2 nanoparticles from growing and result in smaller particle sizes, which is benefited to ORR activity. However, too much selenium oxide would cause severe aggregation of CoSe2 nanoparticles, leading to poor ORR activity.

This research prepared synthesized Pyridine-based polybenzimidazole (PyPBI) with a 4 to 6 molar ratio of 2,6-pyridinedicarboxylic acid (PyDA) and isophthalic acid )IPA). The PyPBI was used as a wrapping polymer of MWCNT and for depositing Pt nanoparticles on the MWCNT (Pt-PyPBI/CNT). The catalysts were physicochemically characterized by transmission electron microscopy (TEM), thermo-gravimetric analysis (TGA), X-Ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The Pt-PyPBI/CNT with Pt loading of ~46 wt.% and Pt particle sizes of about 3-4 nm is used to prepare a PBI/H3PO4 based membrane electrode assembly (MEA) and perform fuel cell test at 160°C. The We demonstrate that the MEA prepared using thePt-PyPBI/CNT catalyst has a higher fuel cell performance than that prepared using a commercial Pt-C.

Two classes of new electrocatalysts for the oxygen reduction reaction (ORR) based on nanoporous/nanostructured carbons are presented. Transition metal-doped ordered mesoporous porphyrinic carbons (M-OMPC) with high surface areas and tunable pore structures have been developed by nanocasting mesoporous silica templates. Among the M-OMPC catalysts, the FeCo-OMPC catalyst exhibited an excellent ORR activity in an acidic medium, higher than other non-precious metal catalysts. It showed higher kinetic current at 0.9 V than Pt/C catalysts, as well as superior long-term durability and MeOH-tolerance. A weakened interaction between oxygen atom and FeCo-OMPC compared to Pt/C as well as high surface area of FeCo-OMPC appear responsible for its significantly high ORR activity. Second example is based on the carbon nanocomposites comprising pure carbon nanotube cores and heteroatom-doped carbon sheath layers (CNT/HDC). The CNT/HDC nanostructures showed excellent ORR activity in an alkaline solution, which is one of the best performances among the heteroatom-doped nanocarbon catalysts in terms of the half-wave potential and kinetic current density. The kinetic parameters of the CNT/HDC nanostructures compared favorably with those of a Pt/C catalyst. In addition, the CNT/HDC also showed high current and power densities when employed as cathode catalysts in alkaline fuel cell.

Platinum group metals (PGM) are the catalyst of choice in a wide variety of catalytic reactions, including the oxygen reduction reaction (ORR). One of the main goals of catalyst development currently is to modify near-surface PGMs, namely platinum, iridium and gold, through size-, strain- and ligand-effects with the support, in order to increase robustness and efficiency while decreasing the cost. We present here our research on tailoring the near-surface electronic structure of the overlayer/support catalytic systems under low-loading limits of PGM overlayers on a wide variety of catalysts for electrochemistry. Surface-limited redox replacement (SLRR) is used for layer-by-layer PGM growth.
Synchrotron-based XPS allowed us to profile the transitions in the electronic structure from the surface down to the adlayer/support interface and beyond. Varying the source photon energy allows us to analyze the electronic structure of the layered system at several penetration depths. Catalyst durability is also a significant aspect for further consideration, with instability oftentimes caused by metal dissolution or corrosion. It is has been shown that Au can have a stabilizing effect on Pt even under high oxidizing conditions and thus can suppress Pt dissolution, resulting in improved durability of the Pt catalysts. This study looks at the durability of Pt monolayer catalysts firstly by subjecting them to aggressive cyclic voltammetry cycling and by examining the activity of the surfaces towards the ORR during potential cycling in an oxygen environment. These two aspects of experiments, spectroscopy and electrochemical tests, are the primary basis for our study.
By analyzing the XPS peak area ratios of the Pt4f and Au4f photoemissions, a relative quantification of the PMG deposit can be achieved. An increase in the ratio of the PMG 4f peaks area to the Au 4f peaks area can be seen as the number of SLRR iterations increases, showing a continuing growth of the adlayer through the SLRR process. Additionally, a negative shift of ~1.5eV in binding energy is measured for the Pt adlayer photoemission between 3 and 6 iterations of the SLRR process at room temperature, showing that Pt is not fully reduced and exhibits cationic intermediaries at low iteration numbers of the SLRR process. With regard to electrochemical durability, samples with an overlayer thickness of 2 monolayers or less show a more dramatic decay in electrochemically active surface area under aggressive cycling, indicating poor durability. However, Pt surface retention is significantly improved once it is at least 3 ML, indicating increased durability due to chemical state and thickness of the surface. The cycling in oxygen-rich media show markedly enhanced currents for the ORR once a 2 monolayer Pt overlayer thickness is achieved, showing the highest activity towards the ORR relative to the amount of platinum present.

Fuel cells and metal oxygen batteries are important electrochemical energy devices. A big problem for the commercialization of these devices lies in the electrocatalysts, particularly for the sluggish oxygen reduction reaction. Platinum is traditionally used as the electrocatalysts for oxygen reduction reaction. But platinum is a rare element and is very expensive. Thus, it is significant to develop platinum-free high-performance electrocatalysts for oxygen reduction reaction. In this paper, I will present the preparation of composites of graphene and conjugated polyelectrolytes and their application as high-performance electrocatalysts for oxygen reaction reaction. The performance is almost the same as that of platinum, and it is significantly better than graphene or composites of graphene and non-conjugated polyelectrolytes.

This research demonstrates a direct printing process of catalyst system fashioned of sub-100 nm metal ring and metal dot catalyst arrays. The stamping platforms used for this printing process are based on the vertically aligned carbon nanoarchitectures with the ring- and dot-shaped tips that are the keystone to determine the printed results (e.g., rings and dots). As a result of the printing process using the ring- and dot-featured stamps, nanoscale metal ring and dot catalysts, made of platinum and gold, are correspondently printed over a large substrate area. An advanced demonstration to understand the fundamental natures of the metal ring and metal dot catalysts as well as to incorporate them into the printable catalytic system is successfully accomplished by applying these printed metal ring and dot arrays into diverse catalyst reactions in acidic and alkaline environment.
The printable nano-sized catalyst systems, made of metal rings and metal dots, were developed for the first time. The vertically aligned carbon-based nanostructures of the ring-shaped tips and the dot-featured tips were employed as the stamps to create the nanoscale ring and dot catalyst arrays. Importantly, the printed nanorings and nanodots were employed into the electrochemical oxidation reactions, which demonstrates catalytic properties caused from the morphology difference of the metal rings and metal dots. It is straightforward that our printing methodology can be highly versatile for fabricating diverse ring and dot arrays made of not only metals but also various organic and inorganic materials, indicating that the printable sub-100-nm ring and dot arrays could play an important role in comprehending the fundamental nature of dot and ring nanomaterials and thus incorporating them into suitable device applications.

Fuel cell current density and voltage are primarily limited by the slow kinetics of the oxygen reduction reaction (ORR) on the cathode. Pt-based catalysts offer high activity for ORR at the low temperatures used in polymer electrolyte membrane fuel cells (PEMFCs), but with prohibitively high cost and poor stability. We engineer carbon nanofiber-supported nitrogen-complexed first-row transition metal (M-N_x-C) catalysts for ORR. Carbon nanofibers (CNFs) are directly grown on stainless steel current collectors. A N-doped carbon overcoat on CNFs is accomplished by electro-initiated polymerization of acrylamide and acrylonitrile. We investigated the effects of presence of metal species during pyrolysis and found the metals to play a key role in the electrocatalysis of ORR. Co yielded the highest onset potential, followed by Cu, Fe, and Zn. The CNF structure shifted the ORR onset potentials by upwards of 100 mV compared to samples without CNFs, and is comparable to Pt activity; the Co-N_x-CNF structure shows a reductive E_1/2 about 70 mV more negative than that for Pt catalyst. Our findings highlight the benefits of binder-free direct electron transport, high surface area, and chemical stability of CNFs coupled with M-N_x-C catalyst sites for ORR. We will discuss the effect of metal on nitrogen heteroatom properties, which in turn affect ORR performance. This research provides new insight in the discovery and optimization of non-precious metal catalysts for low cost, high efficiency fuel cells.

Our previous computational work on the cyclopentene-transition metal (CpTM) functionalized pristine and B-doped nanocarbons (carbon nanotubes and graphenes) demonstrated promising redox properties as an electron donor-recptor in electrochemical system (and great stability). In this work, we report a theoretical study on novel porphyrin-transition metal-nanocarbon complexes (PORTM with TM = Fe, Zn, and Mn) for electrochemical and catalytic applications. The geometries of PORTM/ pristine and B-doped CNTs and graphenes are discussed from potential energy surface scans using density functional theory (DFT) and semi-empirical PM6 methods. The energetic and electronic structural properties are also investigated from the DFT calculations by band structure analyses, natural bond order partial charges, and deformation charge density analyses to explore the stability and application of PORTM-nanocarbon complexes for nanoelectronics. For the electrochemical properties, we calculate the redox potentials and the charge transfer mechanism of PORTM-nanocarbon complexes in different solvents using DFT combined with the conductor-like polarizable continuum model (CPCM) solvation model, and compare them to the CpTM-nanocarbon complexes.

At present, there are strong demand for new battery with large capacity and metal-air battery is attracting much interest. In this study, solid state Fe-air rechargeable battery using LaGaO₃-high oxide ion conducting electrolyte was studied and H₂/H₂O redox mediator shows high performance, including discharge potential, and high capacity. Reaction of this battery proceeds with the following equations at 773 K as we reported.
Air electrode; 1/2 O₂ + 2e- → O^2- (1)
Fuel electrode; H₂ + O^2- → H₂O + 2e- (2)
Fe set chamber; 3Fe + 4H₂O → Fe₃O₄ + 4H₂ (3)
Among the various materials, Ni-Fe-base cermet is highly active anode and stable against charge and discharge for Fe-air battery using LaGaO₃-based oxide ion conducting electrolyte. In particular, La_0.6Sr_0.4Fe_0.9Mn_0.1O₃ (LSFM) and Ce_0.6Mn_0.3Fe_0.1O_0.2 (CMF) were highly effective as oxide used in cermet anode. Stable cycle performance was observed over 30 cycles and energy density of ca. 600 mAh/g-Fe was exhibited with 85 % round trip energy efficiency.

Layered Li₄NiTeO₆ have been synthesized and studied for its possible application in Li-ion batteries with the hope of achieving high capacity through i) the 2e^- redox process associated with Ni⁺⁴/Ni⁺² and ii) oxide ion participation in the redox process as observed with similar Li₄MM&’O₆ oxides.^1-3 The material reversibly reacts with 1.5 Li⁺ at a potential of 4.2 V through a classical insertion mechanism enlisting the Ni⁺⁴/Ni⁺² redox couple. The higher Ni⁺²/Ni⁺⁴ redox voltage observed for Li₄NiTeO₆ (4.2V) as compared to other Ni⁺²-based layered oxides (< 4V) was found to be associated with inductive effect from Te⁺⁶ in Li₄NiTeO₆ as a TeO₆^6- moiety to lower the electron density around Ni⁺² ion. However, the participation of oxide ion in the redox process have not been observed with Li₄NiTeO₆, presumably due to the large separation between Ni⁺⁴ d levels and O2p levels hence limiting the reversible capacity to 110 mAh/g. Though, Li₄NiTeO₆ has limited practical application due to toxic Te, this study open up a way to design better electrode materials with proper tuning of cell voltage and feasibility for anion- cation redox chemistry.
References:
1. M. Sathiya, G. Rousse, K. Ramesha, C. P. Laisa, H. Vezin, M. T. Sougrati, M-L. Doublet, D. Foix, D. Gonbeau, W.Walker, A. S. Prakash, M. Ben Hassine, L. Dupont, J-M. Tarascon, Nat. Mater, 2013, 12, 827.
2. V. Kumar, N. Bhardwaj, N. Tomar, V. Thakral, S. Uma, Inorg. Chem. 2012, 51, 10471.
3. M. Sathiya, K. Ramesha, G. Rousse, D. Foix, D. Gonbeau, A. S. Prakash, M-L. Doublet, K. Hemalatha, J.-M. Tarascon, Chem. Mater. 2013, 25 (7), 1121.

Conversion materials for Li-ion batteries, such as Sb[1] and Sn-based[2] compounds, have attracted much intense scientific attention for their high storage capacities. Among conversion materials, TiSnSb has been developed as a negative electrode for Li-ion batteries. This material can reversibly take up 6.5 Li per formula unit that corresponds to a specific capacity of 580 mAh/g with noteworthy high rate capabilities.[3] As the working potential of TiSnSb is out of the electrochemical window of classical electrolytes like alkylcarbonates mixtures, the formation of a protective and stable passivation film (the solid electrolyte interphase or SEI)[4] is required.
At this time, little information can be found about the formation and composition of the SEI layer on conversion electrodes. With the aim to study the electrode/electrolyte interphase, X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS) were performed on TiSnSb electrodes associated to electrochemical studies. In order to improve the performances of TiSnSb, SEI builder additives (vinylene carbonate VC and fluoroethylene carbonate FEC) were added to the standard electrolyte (1M LiPF6 in EC/PC/3DMC) to modify the SEI composition and morphology.
XPS analysis and EIS results, lead first to the conclusion that the thickness and the resistance of the SEI layer was lower at high cycling rate (4C) than low cycling rate (C/2).[5] Adding additives has also a strong impact on the SEI formation: FEC/VC-containing electrolyte formed a thinner SEI layer and EIS studies supported the same conclusion. In addition to the partial dissolution of the SEI layer occurs during de-lithiation[5], the continuously growing in thickness of the SEI layer upon cycling confirms the dynamic and unstable behavior of the SEI layer already reported for other conversion materials.[6]
In order to overcome the drawback of an unstable SEI, a pyrrolidinium based ionic liquid (IL) was used as electrolyte instead of the alkylcarbonates. It was found not only to improve the cycling performances of TiSnSb electrode but also to decrease the cumulative capacity losses. XPS studies reveal that the nature of the SEI species is responsible to the enhanced cycleability.
In conclusion, an efficient way to improve the cycling performances of TiSnSb, and possibly other conversion electrodes, is to modify the electrolyte formulation. The use of a more stable IL as solvent or co-solvent and adding efficient additives are the best means to stabilize the SEI layer which is strongly related to the specific capacity and cycleability of this type of active material.
1. L. Monconduit et al., J. Power Sources, 107 (2002) 74.
2. J. Wolfenstine et al., J. Power Sources, 109 (2002) 230.
3. H. A. Wilhelm et al., Electrochem Commun 24 (2012) 89.
4. Peled, E. J. Electrochem. Soc. 126 (1979) 2047.
5. C. Marino et al., J. Phys. Chem. C 117 (2013) 19302.
6. M. Stjerndahl et al., Electrochim. Acta 52 (2007) 4947.

Carbon nanotubes have been explored as interconnects in solid acid fuel cells to improve the link between nanoscale Pt catalyst particles and macroscale current collectors. The nanotubes were grown by chemical vapor deposition on carbon paper substrates, using nickel nanoparticles as the catalyst, and were characterized by scanning electron microscopy and Raman spectroscopy. The composite electrode material, consisting of CsH2PO4, platinum nanoparticles, and platinum on carbon-black nanoparticles was deposited onto the nanotube-overgrown carbon paper by electrospraying, forming a highly porous, fractal structure. AC impedance spectroscopy in a symmetric cell configuration revealed a significant reduction of the electrode impedance as compared to similarly prepared electrodes without carbon nanotubes.

Oxide supported catalysts are ubiquitous in industrial, environmental and fuel cells applications. In particular, the oxide supports are of immense importance in solid oxide fuel cells (SOFCs) which utilize the oxygen ion conducting oxides as an electrolyte and a catalyst support in composite electrodes to provide the oxygen ion channel. In this regard, the oxide supports in electrodes of SOFCs have been only studied with respect to the ionic conductivity. However, the interaction between catalysts and oxide supports can give rise to the enhancement of the catalytic activity due to the variation of electronic structure of catalysts due to the orbital hybridization between catalysts and supports. Here, we demonstrate a novel approach to improve the catalytic activity of SOFCs cathode by controlling the oxygen ion conducting oxide supports. The catalytic activity of La0.8Sr0.2MnO3 (LSM) perovskite catalysts is characterized when contacted with different electrolyte supports including yttria-stabilized zirconia (YSZ), scandia-stabilized zirconia (ScSZ), and samaria-doped ceria (SDC). LSM thin films are deposited on the different oxide supports via pulsed laser deposition (PLD) for removal of geometrical uncommonness in terms of porosity and tortuosity and their polarization resistances are measured by the electrochemical impedance spectroscopy (EIS). With these analyses, the contributions of ionic conductivity and catalytic activity enhancement by oxide supports are determined. The optimized composite cathode has been fabricated so that the generic design rule for enhanced composite cathode has been proposed.

The microstructure of porous electrodes has a critical impact on the performance and life-time of solid oxide cells (SOCs). Selective laser sintering (SLS) is a fast, reliable and reproducible process that allows control of the microstructure through sintering together successive layers of metal powder. In this work the use of SLS for an SOC electrode fabrication is presented for the first time by sintering a patterned Ni structure on an YSZ electrolyte. The experiments were carried out using pulsed YAG fiber laser. An optimal set of conditions for electrode fabrication was evaluated by varying the laser power (in the range of 20-200W) and laser speed (in the range of 160-4000mm/s). The electrode microstructure was studied using scanning electron microscope (SEM). The electrical conductivity was measured by the Van der Pauw method. Initial results from these feasibility studies will be reported.

Lanthanum chromite-based perovskite and aliovalent doped zirconia composites offer the potential as active components for high temperature solid state electrochemical devices. The composites can be used as membrane in oxygen transport membrane (OTM) as well as electrodes for solid oxide fuel cells (SOFC) and solid oxide electrolysis cells (SOEC). Intercationic diffusion and formation of secondary compounds due to the interaction between the perovskite and fluorite modifies the thermo-physical and electrochemical properties leading to performance degradation. This study documents our observations on the morphological, chemical and structural changes in the (La0.75Sr0.25)0.95Cr0.7Mn0.3O3 (LSCM) perovskite with yttrium stabilized zirconia (8YSZ) and scandium stabilized zirconia (10ScSZ) during sintering in oxidizing and reducing atmospheres. Significant microstructural changes in the bulk, surface, and interfaces have been observed with respect to partial pressure of oxygen. Inter-cationic diffusion and secondary phase formation are more prevalent in the reducing atmosphere and the interaction is more intense for LSCM and 10ScSZ composite. Possible reaction mechanisms and the role of oxygen pressure responsible for the above changes will be presented.

Durable reversible Solid Oxide Cells (SOCs) capable of operating both as a fuel cell and as an electrolyser may provide the advantage of biogas (CH4 and CO2 mix) upgrade and CO2 reduction in co-electrolysis conditions. However, SOC degradation due to carbon deposition has to be significantly reduced in order to allow for the long term utilization of carbonaceous fuels in SOCs. Currently there is a considerable gap in the understanding of the formation mechanisms and characteristics of carbon formed under negative bias on Ni-based electrodes.
In the present work we have used Raman mapping to investigate the characteristics of carbon formation in SOCs operating in electrolysis mode. These measurements have shown that majority of the carbon forms in close proximity to the electrode-electrolyte interface in porous electrodes. To investigate this process further, laser ablation coupled with electrochemical deposition of Ni was used to prepare patterned electrodes with well-defined triple phase boundaries (TPB). These structures present smooth interfaces that are particularly well suited for analysis with Raman spectroscopy. Analysis of the Raman spectra collected from patterned Ni/YSZ and Ni/CGO electrodes confirm previous observations of superior Ni/CGO resistance to coking and suggests that carbon is dissolving through Ni in both cases. Carbon agglomeration under the Ni is likely to cause electrode delamination leading to irreversible electrode degradation. Maps of the integrated peak area of CGO oxygen vacancies across the electrode surface suggest that oxygen diffusion to the TPB extends up to 100µm in lateral directions. A mechanism of carbon suppression in Ni/CGO system based on CGO electrochemical activity is proposed. We will also provide evidence that suggests that providing a CGO interlayer is effective for carbon deposition mitigation in porous electrodes in CO-CO2 electrolysis conditions.

In the search for SOFC materials which exhibit improved oxide ion conductivity at lower temperatures, attention has recently been focussed towards materials with atypical structural chemistry and diffusion pathways. Oxygen excess materials (such as the Ruddlesden-Popper & Apatite structures) have the potential for interstitial oxide ion conduction with activation barriers to oxygen transport that are typically lower compared to the more common vacancy mechanism found in traditional SOFC materials1,2. An alternative strategy to reduce migration barriers and enhance conductivity in the intermediate temperature regime (4-600°C) is to change the charge carrier from oxide ions to protons, and develop electrolytes that conduct protons from the anode to the cathode3.
Fergusonite structured rare earth niobates (RENbO4) can exhibit both high protonic and oxygen diffusivity depending on the dopant strategy. For example the alkaline earth doped members (RE1-xAxNbO4-δ RE=La, Nd, Gd, Tb, Er A=Ba, Sr, Ca) retain protons as the dominant charge carriers upto 1000°C, with oxygen vacancy diffusion resuming >1000°C 4. The cerium analogue CeNbO4+δ, can incorporate a range of oxygen excess stoichiometries (δ=0, 0.08, 0.25, 0.33) by oxidation of Ce3+ to Ce4+ and exhibits fast oxide ion and electronic conduction5. Unlike other rare earth niobates, CeNbO4+δ conducts via an interstitial type mechanism and adopts either commensurate or incommensurate modulated superstructures showing that symmetry is not necessarily a pre-requisite for fast ion transport.
Here we report the transport properties of Sr2+ doped CeNbO4+δ under oxygen and proton containing atmospheres and show that this new material exhibits total electrical conductivity that is over one order of magnitude greater than the parent material. Full structural and redox characterisation by TOF neutron diffraction and x-ray absorption spectroscopy will be presented. Sr2+ charge compensation occurs largely via cerium oxidation from Ce3+ to Ce4+ as opposed to oxygen vacancy formation. The electrical properties of several compositions of Ce1-xSrxNbO4±δ (x=0.01 to x=0.4) under oxygen and proton containing atmospheres have been investigated; the results show significant enhancement when x>1. Currently variable pO2 and EMF measurements are underway to determine transport numbers for Ce1-xSrxNbO4±δ. It is proposed that the compensation mechanism leads to an enhancement in the electronic domain and potential application as a mixed ionic electronic conductor in SOFC&’s and related applications.
References
[1] SSI, 117, (13-14), 1205-1210, 2006
[2] Chem. Rec, 4, (6), 373-384, 2004
[3] Nat. Mater, 9, (10) 846-852, 2010
[4] Nat. Mater, 5, 193-196, 2006
[5] SSI, 177, (11-12), 1015-1020, 2006

The functionality on SOFC components depends on the structure and dynamics of their materials under operation conditions. Recent progress in instrumentation at neutron and synchrotron radiation sources has made it possible to study SOFC and SOEC systems under realistic operation conditions and understand numerous questions on the physical chemistry of the compounds in interaction with temperature and gases, and the dynamics of charge carriers. I will present a suite of very recent studies where we investigated the sulfur chemistry in SOFC anodes first ex-situ and later under control of the electrochemical potential in-situ with x-ray absorption spectroscopy at the sulfur K-edge. This study is complemented by microstructure investigations with ultra small angle x-ray scattering. The dyamics of protons in ABO3 type rare earth transition metal oxide electrolytes were done under exposure to high water vapor pressure and control of the electrochemical potential by using inelastic and quasi-elastic neutron scattering combined with impedance spectroscopy. The change of the valence band during filling of oxygen defects in these materials was investigated in-situ with high pressure XPS spectroscopy. This allows us to sketch the density of states during materials processing and component operation under realistic conditions.
References:
1. G. Nurk, T. Huthwelker, A. Braun, Chr. Ludwig, E. Lust, R. P. W. J. Struis, Redox dynamics of sulphur with Ni/GDC anode during SOFC operation at mid- and low-range temperatures: An operando S K-edge XANES study, J. Power Sources 2013, 240, 448-457.
2. A.J. Allen, J. Ilavsky, A. Braun, Multi-Scale Microstructure Characterization of Solid Oxide Fuel Cell Assemblies with Ultra Small-Angle X-Ray Scattering, Advanced Engineering Materials 2009, 11 (6), 495-501.
3. Q. Chen, J. Banyte, X. Zhang, J. P. Embs, A. Braun; Proton Diffusivity in Spark Plasma Sintered BaCe0.8Y0.2O3-δ: in-situ combination of quasi-elastic neutron scattering and impedance spectroscopy; Solid State Ionics; in press, http://dx.doi.org/10.1016/j.ssi.2013.05.009

TOF-SIMS has become an important tool for 2D and 3D imaging mass spectrometry of complex materials due to its unique capability to detect elements at a spatial resolution of < 100 nm and at a mass resolution of > 10,000 m/Δm. Among the advantages of TOF-SIMS are a 2 nm sampling depth, parallel detection and collection of the entire mass spectrum at every image pixel, and sensitivities in the ppm to ppb range. The ability to image surfaces having a large degree of topography while maintaining artifact-free chemical imaging is also highly desired; the resulting elemental images provide important information regarding the composition and structure of SOFC, PV and OLED materials. Characterization of specimens to a depth of several microns below the sample surface has become somewhat routine with the use of a sputter ion beam to remove multiple layers of atoms between analysis (chemical imaging) cycles. Nevertheless, there are practical limitations which include preferential or differential sputtering, void spaces and topography that result in a distortion or complete loss of the true 3D chemical distributions. An alternative approach to achieve 3D chemical imaging of chemically complex specimens is to utilize in situ FIB milling and sectioning in conjunction with TOF-SIMS chemical imaginghellip; what we have called FIB-TOF tomography. The advantage of the FIB-TOF approach is that artifacts caused by surface topography, void spaces, and differential sputtering are avoided.
We have used 3D FIB-TOF tomography to characterize 50 mu;m x 50 mu;m x 10 mu;m volumes of as-grown and aged SOFC specimens. The union of successive FIB sectioning and TOF-SIMS analysis cycles for 3D imaging, along with details of the observed chemistry, will be discussed for the analysis of Sr- and Pr-based SOFC samples.

Graphene/MnO2 composites were prepared by hydrazine hydrate-mediated reduction of graphene oxide (GO)/MnO2 at various reduction times to determine the optimal conditions to obtain materials with excellent electrochemical performance. Variations in the oxygen-containing surface functional groups were observed as the reduction time was varied. These changes were found to affect the electrical conductivity and density of nanoneedle MnO2, which impact the surface area and can significantly affect the supercapacitive performance of the composites. Morphological and microstructural characterizations of the as-prepared composites demonstrated that MnO2 was successfully formed on the GO surface and indicated the efficacy of hydrazine hydrate as a reducing agent for GO. The capacitive properties of the graphene/MnO2 electrodes prepared at a reduction time of 28 h (rGO(28)/MnO2) exhibited a low sheet-resistance value as well as a high surface area, resulting in a GO/MnO2 composite with excellent electrochemical performance (371.74 F gminus;1 at a scan rate of 10 mV sminus;1). It is anticipated that the formation of MnO2-based nanoneedles on GO surfaces utilizing the demonstrated 28-h hydrazine-reduction protocol is a promising fabrication method for supercapacitor electrodes.

The last decade has seen considerable importance placed on research in high temperature proton exchange membrane fuel cell (HT-PEMFC) based on phosphoric acid-doped polybenzimidazole (PBI). Many efforts have been made to modify PBI membrane in order to achieve enhanced physiochemical properties required for HT-PEMFC, such as acid doping level, proton conductivity, mechanical strength, and oxidative stability. Cross-linked PBI with porous structure is one of modification approaches, which has been received increased attention recently and is worthy of further investigation.
In this work, we presented a template-leaching method to fabricate PBI asymmetric membranes using ionic liquid as a soft template. It is known that the ionic liquid has a relatively high density. The density difference between the soft template and polymer matrix contributes to the development of the asymmetric porous structure. This method is facile and allows the fabrication of an asymmetric membrane comprising a dense layer and a porous layer with a distinguishable boundary. Further modification using crosslinking is quite simple, as well.
A series of phosphoric acid-doped PBI asymmetric membranes with different porosity have been fabricated. This work confirmed that the porous structure allows PBI membrane to obtain increased acid doping level and enhanced proton conductivity, in accordance with the relative work. The proton conductivity measured at 160°C could reach around 6 × 10-2 S/cm for the PBI asymmetric membranes with high ionic liquid contents. The result of Fenton&’s test revealed that the cross-linking modification could further improve the oxidative stability of asymmetric PBI, even much better than that of dense PBI. Also, we successfully demonstrated fuel cell operation using the fabricated asymmetric PBI as the electrolyte membrane. An enhanced performance was achieved with a peak power density of approximately 295 mW/cm2.

Recent studies revealed the potential of transition metal nitrides as high performance catalysts supports, particularly in proton exchange membrane fuel cell (PEMFC) applications. Metal nitrides with nano-scale particle size and an ordered porous structure are desired for this application. Many reported synthesis of meso/macroporous nitride made use of porous metal oxide as an intermediate for the final product. Due to problems associated with this method, a facile, low temperature synthesis of porous, single-phase, crystalline macroporous chromium nitride and chromium titanium nitride with inverse opal morphology is reported. Characterization using XRD, SEM, HRTEM and TGA were conducted. XPS study was also carried out to provide insights into the chemical states of the elements fabricated using this method. An interconversion of macroporous CrN to Cr2O3 and back to CrN with retaining the inverse opal morphology is also demonstrated. Nitride materials synthesized using this method are also tested using electrochemical measurements after loading with Pt catalysts.

The catalytic activity of disordered binary alloy metal surfaces is investigated for the oxygen reduction reaction (ORR) by generating free energy diagrams and performing calculations on d-band centers of alloys. The disorder was simulated using virtual crystal approximation; then, based on periodic, self-consistent density functional theory (DFT) methods, we calculated adsorption energies of reaction intermediates. Alternative pathway for ORR mechanism, involving proton/electron transfer to adsorbed oxygen and hydroxyl, is considered. The methodology was applied to (111) surface of PdxCu1-x disordered binary alloys, with values different of x concentration. This study found that at the ORR equilibrium potential of 1.23 V, the reactivity of all surfaces is shown to be limited by the rate of OH removal from the surface. Among the surfaces studied, the surface of Pd0.85Cu0.15 shows the highest reactivity and is more active than other non-Pt alloys. These results are in excellent agreement with earlier experimental and theoretical work.

Electrochemical advanced oxidation processes (EAOPs) have attracted increasing attention as a viable alternative to conventional treatment processes. A variety of water-treating anodes have been developed and studied over the past four decades, among which Sb-SnO₂ should be the most practicable in terms of treatment efficiency, cost-competitiveness and environmental non-toxicity. Recently, we reported that Sb-SnO₂ doped with several metals exhibited a range of electrocatalytic activities at circum-neutral pH, among which Ni (II) improved the activity most significantly (by a factor of 7). To examine the cause for the improved electrocatalytic performance of Sb-SnO₂ by Ni doping, the electrochemical nature of Sb-SnO₂ and Ni-Sb-SnO₂ was compared using cyclic voltammetry and impedance analysis. In addition, their electrocatalytic performance was compared for the decomposition of phenol as well as the inactivation of microorganisms (E. coli) in two different electrolytes (Na₂SO₄ vs. NaCl). Compared to Sb-SnO₂, the service lifetime of Ni-Sb-SnO₂ was prolonged by a factor of 9, while its charge transfer resistance was reduced by ca. 65%. Remarkably, the electrocatalytic performance of Ni-Sb-SnO₂ was found to be far superior to that of Sb-SnO₂ regardless of substrate (phenol and E. coil) and electrolyte (sulfate and chloride). The primary reactive species generated at Sb-SnO₂ were found to be hydroxyl radicals ( eta;= 2.4%) in the sulfate electrolyte, whereas hypochlorites (eta; = 0.73%) were primarily generated in the chloride electrolyte. By contrast, ozone was found to be the primary reactive species generated at Ni-Sb-SnO₂ in the sulfate electrolyte (eta; = 9.3%) as well as chloride electrolyte (eta; = 13.6%). This result should call for attention because the Faradaic efficiency for ozone exceeded not only that for hydroxyl radicals (eta; = 3.7%) in the sulfate electrolyte but also that for hypochlorites (eta; = 0.24%) in the chloride electrolyte. In this regard, Ni-Sb-SnO₂ should be a promising anode with great potential for use in a wide range of water treatment processes.

In this study we report the findings on the performance of functionalized Si nanowires as a novel electrode support material for PEM fuel cells. Vertically oriented Si nanowires (VOSNWs) were synthesized using metal assisted electroless chemical etching method, in presence of Ag salts and HF. The study was conducted by varying electrolyte composition. These one dimensional VOSNWs were functionalized with Nb/TiO2 and Pt using both sol gel and ALD techniques. The structural and morphological characterization of the nanostructured material was performed using SEM, TEM, AES, AFM and EDS. Electrochemical performance of functionalized VOSNWs was performed by conducting cyclic voltammetry and oxygen reduction reaction measurements. In addition we also report our investigation on the effect of ultrasonication time for ink formulation on electrochemical performance for same material composition.

Over the past decades, there has been continuous effort to develop intermediate temperature solid oxide fuel cells. Ni-Ce0.8Sm0.2O1.9 anode supported structures attracted most research attention because of their high electrochemical performances at reduced temperatures. However, the Ni-containing anode supporters suffer from poor redox cycling stabilities due to the volume changes arising from the reduction - oxidation cycles. This problem leads to the formation of cracks in the electrolyte layer and, as a result, a performance degradation or even failure of the single cell.
To improve the redox cycling stability of the single cell, we developed a tubular single cell supported by an inert substrate with a configuration of porous yttria-doped zirconia (YSZ) supporter/Ni anode current colloector/Ni-Ce0.8Sm0.2O1.9 anode/YSZ/Ce0.8Sm0.2O1.9 bi-layer electrolyte/La0.6Sr0.4Co0.2Fe0.8O3-δ cathode. The porous YSZ supporter was fabricated by an extrusion method and the cell functional layers were dip-coated on the outer surface of the YSZ supporter. Thicknesses of Ni layers were investigated with respect to the times of dip-coating. Maximum power density and redox cycling stability of the single cells were evaluated with regard to the microstructure features of the Ni layer.
Increasing the thickness of Ni layer reduced ohmic resistance of the single cells, thus, enhancing their electrochemical performances. On the other hand, thick Ni layer led to a large volume change during redox cycles, increasing the stress applied on the electrolyte and reducing the performance stability. Considering the competition effects of these two aspects, an optimum dip-coating time was determined to be two in the present study. The single cell showed a maximum power density of 400 mW/cm2 at 800 °C in hydrogen fuel and the cell maintained 95% of its initial performance after four redox cycles. When incorporating a small amount of Ce0.8Sm0.2O1.9 particles (10 wt.%) into the Ni anode current collector layer, the cell exhibited a significantly improved redox cycling stability. Within ten redox cycles, the cell held 95% of its initial performance, highlighting the advantage of the cell configuration in the present study.

Fuel cell is next generation energy device that converts chemical energy to electrical energy directly without any mechanical conversion processes. Polymer electrolyte membrane fuel cell (PEMFC) has advantages of low operating temperature, highly efficient energy conversion compared with other energy conversion devices and its safe operation. However, there are still some problems such as low activity of cathode catalyst for the oxygen reduction reaction (ORR), water management including flooding in the membrane electrode assembly (MEA) and so on. In the point of view of the water management in the MEA is one of the most important things since the active catalyst sites can be blocked by water produced in the cathode, which results in dramatically decreased performance. In recent decades, there are extensive efforts to resolve the problem with introduction of hydrophobic material such as PTPE or pore forming agent forming larger pores which results in improved water transport. However, these methods have some critical problems including fatal decrease in the electrochemical active surface (EAS) of catalysts and thickened MEA with lower mechanical robustness.
Herein, we address the facile solution to resolve the above problems with introduction of poly(N-isopropylacrylamide) (PNIPAM), which is known for temperature-induced change from hydrophilic to hydrophobic property and volumetric change with shrinkage of polymer chains. With the simple functionalization of NIPAM onto the carbon support of Pt/C using formation of amide bond or UV light exposure in the ink preparation step, we achieved enhanced mass transfer in the high current density region without affecting catalyst(Pt) and polarization curve of the prepared MEA.

Ionic polymer metal composites (IPMCs) are electro-active polymers (EAPs) that show the electromechanical transduction. IPMCs are promising materials as soft actuators in many applications because IPMCs in hydrated state show relatively large displacement under small electric voltage (< 5V). The conventional metal electrode of IPMCs is noble metal such as platinum and gold. Because noble metal is expensive, the non-noble metal such as copper and nickel could be substituted for noble metal. Furthermore, the autocatalytic electro-less plating of nickel could reduce the processing time less than 14 hrs as compared with the conventional processing time (more than 48 hrs). Depending on the fabrication condition such as time, temperature and concentration, the bending response may differ. The bending response depends on not only the electrode properties but also the morphology of interfacial area between the electrode and polymer layer because the interfacial morphology affects capacitance of IPMCs. Among many fabrication conditions, nucleation time effect on the bending response of IPMCs did not investigated. Therefore, we investigated how nucleation time of nickel electro-less plating have influence on the electrode properties, interfacial morphology and bending response of IPMCs.

In situ Ni K edge absorption spectroscopy (XAS) and in situ powder diffrac-
tion were performed to study the fatigue of LiNi0.8Co0.15Al0.05O2 (NCA), a
comercial used cathode material in Li ion batteries. A detailed analysis of the
XRD and EXAFS data shows the presence of an electrochemical inactive phase.
Moreover, this phase was still present at high potentials for the fatigued ma-
terial while it vanished in the pristine material. Futhermore, changes in the
redox process found with cyclic voltammetry and XANES analysis lead to the
conclusion, that the material is oxidized from the outside to the inside of the
particles.

In this work we present EPR measurments done with electrode materials
from Li ion batteries. A comparison of different systems shows, why EPR is
useful studying cathode and anode materials as well as degradation. For the
interpretation of the EPR spectra, high filed measurements, measurments at
different temperatures and in situ measurements are very useful.

Proton exchange membrane fuel cells (PEMFCs) have been known to promising energy devices which is the feasible and efficient technologies for portable, stationary and transportation applications. However, high cost and low durability of their electrocatalysts hinder the widespread commercialization of PEMFCs. Alkaline anion exchange membrane Fuel cells (AEMFCs) have the potential as an alternative to PEMFCs. Under alkaline conditions, the kinetics of the oxygen reduction reaction (ORR) on the cathode are enhanced compared to acidic environment, leading to improve fuel cell efficiency. Also, the facile kinetics of ORR can reduced need for high loadings of precious metal catalysts and allows the use of nonprecious metals as a catalysts, resulting in reducing the cost of the fuel cell. Moreover, it has fuel flexibility due to low overpotential for hydrocarbon fuel oxidation and reduced fuel cross over. Despite of these advantages, currently achieved power densities of AEMFCs still lower than PEMFCs. To improve the performance, recent studies have focused on development of anion exchange membrane, ionomer and electrode design. However, there is a lack of research on the various aspects like operating condition, water management, and membrane-electrode-assembly (MEA) for realizing the maximum performance of AEMFCs. In this study, to maximize the performance of AEMFCs with nonprecious catalysts, we investigate the key factors that influence the performance of AEMFCs, especially focused on controlling the material used in fuel cell.

Graphene consists of two dimensional one-atom-thick planar sheets of sp2 bonded carbon atoms, receives tremendous attention as a new material due to its excellent properties. In the area of fuel cell electrocatalysts, graphene has been used as a support material and appeared better performances than other carbonaceous materials. [1]
In this work, we synthesized different sizes of reduced graphene oxide (RGO) sheets via wet-chemical oxidation subsequent thermal reduction process, and followed by size fractionation procedure by controlling pH of the graphene oxide (GO) solution. Pt/RGO catalysts were prepared via impregnation of Pt onto the size selected RGO supports. The physicochemical characteristics of the obtained materials were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The electrochemical properties of Pt/RGO catalysts were measured by cyclic voltammetry (CV) for methanol electro-oxidation in an acidic medium.
Acknowledgement
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2013029776 (Mid-career Researcher Program)), the Global Frontier R&D Program on Center for Multiscale Energy System funded by the National Research Foundation under the Ministry of Science, ICT & Future, Korea (0420-20130103), and Core Technology Development Program for Next-generation Solar Cells of Research Institute for Solar and Sustainable energies (RISE), GIST.
Reference
[1] S. M. Choi, M. H. Seo, H. J. Kim, and W. B. Kim, Carbon 2011, 49, 904-909.

Carbon nanotubes represent an interesting material for the formation of 3D architectures on electrodes. By surface modification the properties can be adjusted in such a way that direct interaction with redox enzymes becomes feasible. This will be illustrated here for two enzymes and applications of such systems in a biofuel cell.
In a first system the pyrroloquinoline quinone dependent glucose dehydrogenase (PQQ-GDH) from Acinetobacter calcoaceticus is covalently bound to an electropolymerized thin polyaniline based film on multi-walled carbon nanotubes (MWCNT) modified gold. Electropolymerisation was performed in a mixture of 2-methoxyaniline-5-sulfonic acid and m-aminobenzoic acid. The glucose oxidation on this anode starts at -0.1V vs. Ag/AgCl and current densities up to 500mu;A/cm^2 can be achieved at a rather low potential. In combination with a cathode (500mu;A/cm^2 , 0.5V vs. Ag/AgCl ) where the oxygen reducing bilirubin oxidase (BOD) is covalently coupled to thiol modified MWCNTs a biofuel cell with a cell potential of 680±20mV and a maximum power density of up to 65mu;W/cm^2 at 350mV vs. Ag/AgCl in the presence of glucose can be established.
The second fuel cell uses MWCNT based bucky paper as electrode material. For the anode development it was modified with poly(3-aminobenzoic acid-co-2-methoxyaniline-5-sulfonic acid). Subsequently the PQQ-GDH was covalently coupled to the polymer. The glucose oxidation of this electrode starts at a potential of -0.1V vs. Ag/AgCl and achieves a current density of 700mu;A/cm^2 . As cathode PQQ modified bucky paper with covalently bound BOD was applied. For this electrode a start potential of about 0.5V vs. Ag/AgCl and a maximum current density of 840mu;A/cm^2 can be observed. The biofuel cell resulting from the bucky paper electrodes shows current densities up to 97mu;W/cm^2 in a 10mM glucose solution.

Keggin-type heteropolyacids (HPAs) exhibit potential application as electrocatalysts. HPAs, notably molybdovanadophosphates, could provide platinum-free technology for innovative low cost hydrogen fuel cell systems. For example, the Flowcath® system developed by ACAL Energy Ltd uses an aqueous HPA solution. This liquid catalyst flows through the cathode part of the fuel cell, acting as the oxygen reduction catalyst and simultaneously promotes electron transfer. The HPA catalyst is regenerated simply by exposure to air after being pumped around the fuel cell stack. Hence, HPAs exhibits fast, reversible, multielectron redox behaviour under ambient conditions.
However, development of the HPA catalyst/electron mediator is vital to improve the fuel cell performance. This is important in order to meet the power output demands for automotive applications, thus providing a commercially viable source of renewable energy. Therefore, this study involves the synthesis of water-soluble Keggin-type HPAs with increased solution conductivity and improved efficiency of oxygen reduction reaction at the cathode.
A series of water-soluble molybdophosphates doped with varying concentrations of vanadium, and one other first row transition metals, have been synthesised. The HPAs have been characterised via several spectroscopic and diffraction techniques. The structural elucidation techniques have been studied in parallel with cyclic voltammetry experiments, in order to reveal the location of the dopant metals within the Keggin structure. These techniques enable the mechanism of electron transfer during the cathode redox reaction to be investigated and understood.
Preliminary results with novel HPA compounds demonstrate a positive shift in reduction potentials, showing potential for improved efficiency of redox reaction at the cathode. Advanced electrochemistry experiments are focused on distinguishing the electron transfer kinetics, electron stoichiometry and diffusion coefficients of novel Keggin-type HPA solutions. These HPAs have potential application as the liquid catalysts in fuel cell systems, such as Flowcath®, therefore will be tested for fuel cell performance.

Titanium nitride (TiN) coatings were deposited on 316L stainless-steel substrates by ion plating with the help of inductively coupled plasma (ICP), and the effect of ICP power on the evaporated TiN coatings was investigated. The electrochemical and electrical properties of the coating were examined for application to a polymer electrolyte membrane fuel cell (PEMFC). The interfacial contact resistance (ICR) value was 11 mOmega;cm^2 at a compaction force of 150 Ncm^-2, which is remarkably low compared to that of TiN coated samples prepared by conventional sputtering method. However, the corrosion resistance was not improved with the corrosion potential and current density values of 0.2 V (vs. SCE) and <5×106 Acm^2 at 0.6V, respectively. It was shown that the processing time for the TiN deposition can be considerably reduced and the contact resistance of the coating was reduced by applying the ion plating method. It was suggested that the corrosion resistance of the bipolar plate could be improved by TiCrN coatings instead of TiN coatings.

Water-oxygen electrochemistry is a key element of renewable energy technologies such as water electrolysis, fuel cells, and metal-air batteries. Known for its sluggish kinetics, two main reactions are involved: oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). ORR is the ubiquitous cathode reaction in fuel cells, while OER is the highly controlling anode reaction in electrolysis cells, which both are known to limit the efficiency of the energy renewable devices. While integrating both reactions into a single cell module is definitely beneficial, an efficient catalyst for both reactions is still needed. The best catalysts discovered so far, however, are selective only to one specific reaction and extremely expensive, such as Pt, RuO2, and IrO2. Thus, there is a motivation to find cheaper alternative electrocatalysts, preferably with bifunctional activity, to replace these precious metals.
Herein, we introduce a facile process to create gently reduced graphene oxide incorporated into cobalt oxalate microstructures (CoC2O4/gRGO) and demonstrate its excellent and stable electrocatalytic activity in both ORR and OER. CoC2O4/gRGO exhibits synergistic effect towards ORR, via a quasi-four-electron pathway. The possible mechanisms for the catalytic reactions were studied using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Our results suggest that gRGO catalyzes the ORR via the substituted N-functional groups. On the hand, activity for OER is exclusively due to CoC2O4 through the O-functional groups, while there is a good indication that gRGO provides high electrochemical stability for the composite. We believe that this study can contribute to the present understanding of metal-graphene composition, to further develop alternative catalysts for fuel cells and metal-air batteries.

It is essential that cathode active layers for PEMFC contain three interpenetrating networks providing high electrical and ionic conductivity, and rapid gas transport to a high surface area catalyst. These networks must continue into the diffusion media, tuned to allow fast gas and water transport while preventing flooding.
Though the desirable properties of electrodes are well understood, fabrication of optimal systems is difficult. We report the use of a complete electrode structure, both active layer and diffusion media, fabricated entirely from multi-walled nanotubes (MWCNT) using a simple filtration method. This simple method allows the production of a full electrode directly from suspension and affords excellent control over layer thicknesses.
Carbon nanotubes have high conductivity, are naturally hydrophobic and corrosion resistant, making them excellent materials for fuel cells. We take advantage of the range of diameters available to make a structure with graduated porosity and roughness. 10nm diameter MWNTs are used as catalyst supports and progressively larger diameters are added to make a complete fuel cell electrode with graded porosity.
Filtration fabricated MWCNT diffusion media have shown good properties in ex-situ testing; a porosity of 88%, an in-plane electrical resistance of 0.42 Omega; square-1 and a superficial contact angle of 158° all compare favourably with traditional diffusion media. Preliminary fuel cell cathode testing using an un-optimised Pt/C active layer with a low (0.2 mg cm-2) loading of Pt gave a performance of 480 mA cm-2 at 0.4 V with H2/O2 at 25 degrees C.

The oxygen reduction reaction (ORR) at the cathode of fuel cells plays a key role in controlling the performance of a fuel cell, and efficient ORR electrocatalysts are essential for practical applications of fuel cells.1 In addition to fuel cells, oxygen reduction electrodes also have found many other applications, such as in electrolyzer and metal-air batteries. Usually, platinum is considered to be the best catalyst for ORR but it, in fact, suffer from sluggish kinetics and insufficient performance durability. Most importantly, platinum remains an expensive metal of low abundance. Recent intensive research efforts in reducing or replacing Pt-based electrode in fuel cells have led to the development of new ORR electrocatalysts. Several types of non-platinum catalysts have been proposed such as transition metal chalcogenides, transition metal oxide, metal macrocycles, and nitrogen-doped carbon structure. Among them, pyrolyzed metal macrocycles has attracted the most attention over the years because of respectable stability and high ORR activity. However, the physicochemical properties and active site structures remain unclear.
In this study, a pyrolyzed cobalt-polypyrrole-CNT catalyst was synthesized by chemical polymerization and thermal treatment as a non-precious metal catalyst for oxygen reduction reaction (ORR). Before the pyrolysis, the coordination of Co-N was optimized by EXAFS analysis. The structural characterization of catalyst was carefully carried out by XRD, Raman spectroscopy, FT-IR, FE-SEM, HR-TEM, XPS, and EXAFS. The results revealed that cobalt ion was successfully immobilized around the nitrogen atoms of polyaniline. And, it was found that cobalt species moved to the inside of pyrolyzed polymer matrix during the thermal treatment with changing the concentration of nitrogen. Also, the electrocatalytic activity was dependant the N/Co ratio. The interaction between cobalt and nitrogen atoms should play an important role to enhance the activity of catalyst. The interaction between cobalt and nitrogen atoms should play an important role to enhance the activity of catalyst.

There have been extensive research efforts focusing on developing technologies for renewable electricity, particularly solar photovoltaics and wind turbines. However, the intermittent and localized nature of wind and solar energy necessitates the development of a cost-effective way to balance energy supply and demand and to deliver electricity from remote places to cities. The short-term option is the electricity grid; however, it can only support intermittent renewable electricity in a stable fashion up to approximately 20 % of grid capacity which means that fossil resources would still account for the remaining 80 % of grid electricity. Clearly, the development of cost-effective energy storage devices is needed to establish a path toward fossil-free energy.
Pumped hydro currently dominates grid-scale energy storage due to its low cost but is hindered by a lack of suitable geographical sites. Hence, there has been interest in developing alternative cost-effective energy storage technologies that can be rapidly scaled-up. Regenerative fuel cells (RFCs) are interesting candidates: a RFC is an electrochemical energy storage and conversion device that typically uses H2 as an energy carrier. RFCs possess high specific energies, enjoy economies-of-scale advantages, are modular in nature, and use only environmentally friendly and inexpensive reactants. However, RFCs are currently too expensive to compete with existing energy storage technologies.
Herein, we demonstrate a prototype alkaline exchange membrane unitized RFC (AEM-URFC) that stores energy based on electrochemical interconversions among H2O, H2, and O2, with the key development of having done so in a low-temperature, precious-metal free device operating at low temperatures while avoiding the use of precious metal catalysts. The prototype device we have developed obtains round trip efficiencies of 34-40 % at 10 mA/cm2 over 8 cycles, with a peak power density of 17 mW/cm2 in fuel cell mode. This report of a precious-metal free AEM-URFC opens up new possibilities for enabling cost-effective and widespread deployment of renewable electricity.

Lithium ion batteries are becoming more important because of their high energy density and design flexibility. The capacity of these batteries is usually cathode limited, so it follows that increasing the capacity of the cathode is essential to raise the performance of such batteries. In this work fractal dimension study is used to understand the behavior of a Li2TiO3, as a way to improve their uses in energy storage. X-ray, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) analysis were used to analyze changes on the surface of samples. Digital image analysis allows the study of fractal dimension, from the current results, the distinctive characteristics of the surfaces for each sample may be obtained, making it possible to predict a future behavior of the samples. MATLAB software FRACLAB 2.03 developed by INRIA (http://www.irccyn.ec-nantes.fr/hebergement/FracLab) was used as a tool. Graphite powders remained on the surface of the Li2TiO3 by sol-gel method.

Developing highly active catalyst for oxygen reduction reaction (ORR) to optimize the performance of fuel cells have long been a crucial issue for future generation of renewable energy application. Meanwhile, the high cost of Pt-based catalysts has hampered the widespread application of fuel cells. In this context, much effort has been devoted to developing carbon-based Pt-free or even metal-free catalysts for ORR due to their low-cost, high electrocatalytic activity and selectivity, as well as excellent durability.
Herein, we successfully synthesized Nitrogen-doped Porous Reduced Graphene Oxide (NRGO) with high surface area via KOH activation to generate pores followed with thermal reaction between ammonia gas and reduced graphene oxide.
The nitrogen cotent of the porous RGO reached 6.4% via ammonia gas treatment at 900 °C while the highest nitrogen cotent of the porous RGO could be as high as 10.1% via ammonia gas treatment at 1000 °C. NGRO exhibited a high surface area of 526 m2 g-1 and a pore diameter of 1.4 to to 8.8 nm.
We found that he NRGO obtained by ammonia gas treatment at 900 °C displayed an excellent ORR performance with current density of 6.83 mA cm-2 at -0.4V in alkaline solution which outperformed the platinum-based catalysts.

Scarcity of fossil fuel resources has led an increased emphasis on hydrogen as a major player in global energy landscape. Hydrogen is produced primarily from steam reforming of natural gas or from other fossil fuels, releasing CO2 in the process. Proton exchange membrane (PEM) electrolyzers can split water into hydrogen and oxygen.[1] When coupled with renewable electricity sources, (PEM) electrolyzers provide a sustainable path to hydrogen production. The hydrogen evolution reaction (HER) takes place at the PEM electrolyzer cathode and has traditionally been catalyzed by platinum, the most active known HER catalyst in acid.[2] Though Pt is extremely active, it is also an expensive rare earth element. To decrease the cost of PEM electrolyzers, there is a need for highly active non-precious metal catalysts.[3]
Molybdeum disulfide (MoS2) is a potential replacement for Pt due to its low cost and high activity. Previous studies of MoS2 have shown that only the edge sites are active for the HER. [4, 5] In order to develop a highly active catalyst, it is necessary to expose a high density of MoS2 edge sites.
In this study, MoO3 was electrodeposited[6] onto carbon paper gas diffusion electrodes (GDE) and converted to MoS2 by an H2S treatment. The GDEs were characterized in an electrochemical cell for catalytic activity and electrochemically active surface area (ECSA). Initial polarization curves of the electrodeposited catalyst showed poor activity for the HER. However, it was shown that electrochemically anodizing the carbon paper support before electrodeposition produced extremely active GDEs. The MoS2 gas diffusion electrodes were tested in a PEM electrolyzer and the cell activity was compared with an electrolyzer that utilizes a Pt cathode. The MoS2 cathode cell showed about a 200 mV offset from the Pt cathode cell.
Continuing work focuses on improving the activity of the MoS2 electrode. One technique will include impregnating MoS2 nanoparticles on XC-72 carbon black and loading a catalyst ink directly onto the carbon paper GDE.
References:
1. Carmo, M., et al., International Journal of Hydrogen Energy, 2013. 38(12): p. 4901-4934.
2. Norskov, J.K., et al., Journal of The Electrochemical Society, 2005. 152(3): p. J23-J26.
3. Ayers, K.E., et. al., ECS Transactions, 2012. 41(10): p. 15-22.
4. Hinnemann, B., et al., Journal of the American Chemical Society, 2005. 127(15): p. 5308-5309.
5. Jaramillo, T.F., et al., Science, 2007. 317(5834): p. 100-102.
6. McEvoy, T.M. et. al., Journal of materials research, 2004. 19(2): p. 429-438.

One of the main concerns in the popularization of fuel cell technology is a replacing Platinum group metal (PGM) based catalyst for oxygen reduction reaction (ORR) with inexpensive, more abundant non-precious metal catalysts. A progress in development of ORR electrochemical catalyst is summarized as four steps: (1) decreasing pure Pt usage and increasing surface areas by introduce support, (2) Pt-based alloys for enhancement of ORR activity and stability by nano-structuring or alloying, (3) replacing Pt-based catalysts with cheaper and non-PGM compounds, (4) N-doped carbon based materials such as graphitic carbon nitride (g-CN). One of the most promising candidates is transition metal nitrogen materials like metal-N4 macrocycles, but there are still some challenges in both their catalytic activity and stability.
Recently, g-CN has proven to be effective as multifunctional catalyst for various applications, such as photochemical splitting of water, mild and selective oxidation reactions, super-active hydrogenation reactions, and ORR for fuel cells. Particularly, the ORR catalytic property of g-CN is considered to be an important subject for clean energy conversion and storage. This is because g-CN has many advantages compared to traditional Pt catalyst including (1) relatively low-cost and more abundance, (2) better stability toward CO poisoning, (3) higher methanol tolerance, and (4) possibility to obtain a variety of nanostructure using templating method. In addition, g-CN has higher nitrogen content and more active reaction sites than other N-carbon materials to serve as a practicable metal-free ORR electrocatalyst.
Here we report solution based facile and gram-scale production of g-CN hybrid composite, via a simple process without high-pressure. The resulting composite material exhibited competitive ORR catalytic activity and stability compared to a commercial Pt/C catalyst.

Cost effective hydrogen evolution reaction (HER) catalysis without using precious metallic elements is a crucial element for clean energy production. Molybdenum sulfide is suggested be a promising candidate for such purpose, but its catalytic performance is inherently limited by the sparse catalytic edge sites and poor electrical conductivity. We report novel hybrid catalysts composed of amorphous molybdenum sulfide (MoSx) layer directly bound at N-doped carbon nanotube (NCNT) surfaces. Owing to the high wettability of N-doped graphitic surface and electrostatic attraction between thiomolybdate precursor anion and N-doped sites, nanoscale thick amorphous MoSx layers are readily deposited at NCNT surface under low temperature wet chemical process. The synergistic effect from the dense catalytic sites of amorphous MoSx and highly electro-conductive NCNT framework attains the excellent HER catalysis with onset overpotential as low as 75 mV and small potential of 110 mV for 10 mA/cm2 current density, which is the highest HER activity of molybdenum sulfide based catalyst ever reported thus far.

In recent years, the market for portable electronic devices, electric vehicles and hybrid electric vehicles has been growing rapidly. These products require more high-performance energy-storage systems such as supercapacitors, which are electrochemical energy-storage devices that are ideally suited to the rapid storage and release of energy in applications requiring a short load cycle and high reliability, such as energy capture sources, including load cranes, forklifts, and the brakes of electric vehicles. In addition, supercapacitors can play an important role in complementing the energy storage functions of batteries and fuel cells by providing back-up power supplies to protect against power disruptions.
Activated carbons are the most widely used electrode materials for the electric double-layer type of supercapacitors because of their large surface area, low cost, nontoxicity and easy processability. However, their low energy storage capacity and restricted rate capability are demerits with regard to their use as an electrode material for supercapacitors.
In this study, we propose a method of overcoming the demerits of activated carbon such as the low energy storage capacity and restricted rate capability by using functionalized activated carbon particles (FACs) and a cross-linkable polymeric binder (i.e. carbon composite).
Acknowledgement
This study was supported by a grant (B551179-10-01-00/ KM3000/ NK167D/ SC0860) from the cooperative R&D Program funded by the Korea Research Council Industrial Science and Technology, Republic of Korea.

The economic conversion of CO2 into more reduced species such as alcohols or hydrocarbons would: create fuel, generate feedstocks for industrial chemicals and store electricity from renewable technologies such as solar cells or wind turbines. Almost all metals have the ability to catalyze the electrochemical reduction of carbon dioxide at room temperatures, however, most do so with low current efficiencies or high overpotentials, when producing carbon-based fuels that are conventionally made from petroleum [1].
We studied several polycrystalline transition metals: Au, Ag, Zn, Cu, Pt, Fe, and Ni for CO2 electroreduction with a custom-made electrochemical cell, designed with a high surface-area to-volume ratio for enhanced sensitivity for liquid products. Constant potential experiments were conducted for an hour, with multiple repeats, across various potentials. Gas products were detected with a gas chromatograph at regular intervals during the experiment. Liquid products were detected via 1H Nuclear Magnetic Resonance at the end of the tests.
Hydrogen, carbon monoxide, formate, methane and ethylene were the major gas products formed on the surfaces, which is consistent with previous studies. The minor products included a range of alcohols, aldehydes, ketones, esters and hydrocarbons, some which have not been detected previously in literature. This presentation discusses trends in the metals selectivity and activity to CO2 electroreduction based on proposed mechanisms [2,3]. Our data suggest that CO binding energies correlate with activity
References
1. Azuma, M., et al., Electrochemical Reduction of Carbon Dioxide on Various Metal Electrodes in Low-Temperature Aqueous KHCO3 Media. Journal of The Electrochemical Society, 1990. 137(6): p. 1772-1778.
2. Peterson, A.A., et al., How copper catalyzes the electroreduction of carbon dioxide into hydrocarbon fuels. Energy & Environmental Science, 2010. 3(9): p. 1311-1315.
3. Peterson, A.A. and J.K. Noslash;rskov, Activity Descriptors for CO2 Electroreduction to Methane on Transition-Metal Catalysts. The Journal of Physical Chemistry Letters, 2012. 3(2): p. 251-258.

A class of new non-precious metal catalysts for oxygen reduction reaction (ORR), ordered mesoporous porphyrinic carbons (M-OMPC; M = Fe, Co, or, FeCo), was synthesized via a nanocasting method, using mesoporous silica as a template and metalloporphyrins as a precursor, respectively. Among the family of M-OMPC catalysts, the Fe and Co co-doped OMPC (FeCo-OMPC) showed an extremely high electrocatalytic activity towards ORR in acidic media. In addition, the most active FeCo-OMPC catalyst showed higher kinetic current at 0.9 V than Pt/C catalyst, as well as superior long-term durability and methanol-tolerance. Density functional theory calculations coupled with extended X-ray absorption fine structure analysis revealed a weakening of the interaction between oxygen atom and FeCo-OMPC compjavascript:setNextPage('ABSTRACT_CAT_PRES');ared to Pt/C. This effect and high surface area of FeCo-OMPC may account for its significantly high ORR activity.

An ionic liquid (IL)-driven, facile, scalable route to new carbon nanostructures comprising pure carbon nanotube cores and heteroatom-doped carbon sheath layers (CNT/HDC) has been developed. The design of the CNT/HDC nanocomposite allows for combining electrical conductivity derived from the CNTs with the catalytic activity of the heteroatom-containing HDC sheath layers. The CNT/HDC nanostructures showed excellent electrocatalytic activity for the oxygen reduction reaction (ORR) in an alkali medium, evidenced by their high half-wave potential. The ORR activity of CNT/HDC nanostructures is one of the best performances among the heteroatom-doped nanocarbon catalysts in terms of half-wave potential and kinetic current density. The kinetic parameters of the CNT/HDC nanostructures, including 4-electron selectivity and exchange current density, compared favorably with those of a Pt/C catalyst. The CNT/HDC nanostructures also exhibited superior long-term durability and poison-tolerance relative to Pt/C. In addition, the CNT/HDC nanostructures showed high current and power densities when employed as a cathode catalyst in alkaline fuel cell, which sheds light on their practical applicability.

Ordered mesoporous carbon arrays embedding molybdenum disulfides nanosheets (MoS2@OMC) have been prepared by sequential formation of carbon and MoS2 nanostructures inside the nanopores of mesoporous silica templates followed by etching of the latter. This design of MoS2@OMC structures combines the electrical conductivity of carbon frameworks as well as the formation of MoS2 nanosheets with a high density of edge sites. The MoS2@OMC revealed static edge/basal ratio regardless of a change of layer number in MoS2 nanosheets. Significantly, MoS2@OMC with few layers of MoS2 nanosheets exhibited very high electrocatalytic mass activity for hydrogen evolution reaction (HER). This design of hybrid structure can be extended to other metal dichalcogenides.

Hydrogen production via solid oxide electrolysis cells (SOECs) by using carbon-free electrical energy has received much attention. Yttria-stabilized zirconia (YSZ) has been widely studied as a solid electrolyte in SOECs. Water splitting under operation of SOECs requires oxygen vacancies at the cathode surface. This study reports the population profile of oxygen vacancies at low-indexed YSZ surfaces by using ab initio thermodynamics calculations. The oxygen vacancies at the top-most (111) surface were less stable than those at the second layer from the surface. A space charge layer model was employed to evaluate the population profile near the (111) surface, based on the segregation of the oxygen vacancies at the second layer. Other low-indexed surfaces, such as (100) and (110) surfaces, were also evaluated to obtain a big picture of the overall surfaces of YSZ.

Cyclic voltammetry or CV is a type of potentiodynamic electrochemical measurement conducted at stagnant conditions. In a cyclic voltammetry experiment the working electrode potential is ramped linearly versus time like linear sweep voltammetry. Cyclic voltammetry takes the experiment a step further than linear sweep voltammetry which ends when it reaches a set potential. When cyclic voltammetry reaches a set potential, the working electrode's potential ramp is inverted. This inversion can happen multiple times during a single experiment. Cyclic voltammetry is generally used to study the electrochemical properties of an anodic reactions [1, 2].In an effort to determine the specific activity of oxygen reduction reaction at the cathode of fuel cell many investigators [3-5] utilize cyclic voltammetry in dilute 0.1 mole/liter HClO_3 to determine the under-potentially deposited hydrogen H_upd in the potential range between 0.05 and 0.4 volts from the following cathodic reaction
H^+ + e^- = H_upd [1]
This supposed to give the electrochemical active surface area (ECSAs) of the cathode electrode. It is obvious that `reaction 1at such low concentration of hydrogen ions (0.1 moles /liter) and at stagnant conditions is controlled by diffusion limitation. The objective of this comment is to show that misleading results may results from using cyclic voltammetry for cathodic reaction especially at low concentration of electro-active species.
[1] Bard, Allen J.; Larry R. Faulkner (2000-12-18). Electrochemical Methods: Fundamentals and Applications (2 Ed.). Wiley.
[2] H. Jürgen. Agnew. Chem. Int. Ed. 23 831 1984
[3] Stamenkovic et al. Science 315, 493 January 2007.
[4] Yu et al. Agnew. Chem. Int. Ed. 50 2733 2011.
[5] Stamenkovic et al. Nature Materials 6, 241, 2007.

In this research polybenzimidazole (PBI) and grafted side chain phosphonate PBI-EPA were synthesized, the polymer structures, grafting percentage, thermal stability and molecular weight were identified by FTIR, NMR spectroscopy, TGA (Thermogravimetric Analysis) and GPC (Gel Permeation Chromatography). The various ratios of PBI/PBI-EPA blended membranes were fabricated. The phosphoric acid doping level of blended membranes was increased when the blended weight percentage of PBI-EPA enhanced. Membrane electrode assemblies (MEAs) of PBI/PBI-EPA membranes had a better PEMFC (proton exchange membrane fuel cell) performance more than pure PBI membrane at 160 degree C.

Redox flow batteries (RFBs) are attractive energy-storage devices, which need to be combined with distributed power generation sources for renewable energy systems and peak-power energy controls. For the redox flow batteries, the redox couples (for oxidation-reduction reactions) and the high performance electrolyte (liquid electrolyte and membranes) are crucial materials for obtaining higher energy densities and capacities.
Membranes for RFBs require the following properties: higher ionic conductivity, lower permeability, chemical stability, and mechanical properties. Nafion membranes of perfluorinated sulfonated copolymer have been widely used for vanadium RFBs. However, Nafion exhibited higher permeability of vanadium ions, which reduces the energy densities due to mixed electrochemical reactions. In this study, the commercialized Nafion membranes were modified to obtaining hybrid membranes. The sulfonated inorganic materials were impregnated in the clusters inside Nafion membrane through the sol-gel reactions. Hybrid membranes exhibited comparable ionic conductivity of 0.09 S/cm and lower permeability of 30% of Nafion membrane. The sulfonated inorganic materials reduced the permeation of vanadium ions without reducing of ionic conductivity.

Proton conductivity of the natural diatomite was studied by ac complex impedance technique. At room temperature, the highest proton conductivity was found to be 4.5 x 10-7 S/cm. By hydrating the diatomite, the proton conductivity was increased to two orders of magnitude higher. The room temperate proton conductivity of the hydrated diatomite (5.5 x 10-5 S/cm) was comparable to other hydrated solid proton conductors. Based on these results, the natural diatomite could be used as solid proton conductor for various electrochemical applications such as fuel cells, gas sensors, humidity sensors, and pH sensors.

The ability to intercalate guest species into the van der Waals gap of two-dimensional (2D) layered materials affords the opportunity to engineer the electronic structures for a variety of applications. Here we demonstrate the continuous tuning of layer vertically aligned MoS₂ nanofilms through electrochemical intercalation of Li⁺ ions. By scanning the Li intercalation potential from high to low, we have gained control on multiple important material properties in a continuous manner, including tuning the oxidation state of Mo, the transition of semiconducting 2H to metallic 1T phase, and expanding the van der Waals gap until exfoliation. Using such nanofilms after different degree of Li intercalation, we show the significant improvement of the hydrogen evolution reaction (HER) activity. A strong correlation between such tunable material properties and HER activity is established. This work provides an intriguing and effective approach on tuning electronic structures for optimizing the catalytic activity.

The efficiency of H2 production by electricity-driven and solar-driven water electrolysis is limited by the high kinetic overpotential of the oxygen evolution reaction (OER). Single transition metal oxide OER catalysts such as CoOx or NiOx have been extensively studied to understand the mechanisms involved in oxygen evolution. In certain cases it has been found that mixed-metal binary, ternary, or quaternary oxides have higher activity than single metal counterparts. We find that the introduction of Fe into Ni-based catalysts results in a dramatic increase of OER activity (1). However, poorly defined surface structures, compositions, and mass transport during OER makes understanding the structure-activity relationships in many of these mixed metal systems very difficult. The goal of this study is to better understand the structure-composition-activity relationships by analyzing how the morphological, electronic and structural properties change as Fe is introduced into Co1-xFex(OH)2 catalysts. This work is also relevant to understanding recent Ba0.5Sr0.5Co0.8Fe0.2 perovskite catalysts that leach the Ba2+ and Sr2+ to form Co-Fe surface species that are the active catalyst (2),(3).
Thin films were electrochemically deposited from Co(NO3)2/FeCl2 solutions. Scanning electron microscopy images reveal a porous platelet-like structure that should allow for facile ion transport throughout the film. Increases in Fe content resulted in higher activity and higher Co2+/3+ oxidation potentials. This data supports the hypothesis that Fe exerts an electron-withdrawing effect on Co. In both pure Co(OH)2 and Co1-xFex(OH)2 OER catalyst thin films, we find with ex situ x-ray photoelectron spectroscopy that the coordination of the Co changes as it is cycled in basic conditions. Upon extended cycling we see a shift in structure from Co(OH)2 to Co3O4/CoO(OH) and a net decrease in the apparent turnover frequency (TOF). This decrease in activity is mirrored by a subsequent decrease in the size of the Co2/3+ redox waves. Normalized to the number of active Co sites, the Co1-xFex(OH)2 OER catalyst thin films have intrinsic TOFs similar in magnitude to that measured for the high-activity Ni1-xFex(OH)2 catalysts. These results indicate that cycling affects the availability of Co active centers, but not the intrinsic activity of each individual Co site.
(1) Trotochaud, L.; Ranney, J.K.; Williams, K.N.; Boettcher, S.W. Solution-Cast Metal Oxide Thin Film Electrocatalysts for Oxygen Evolution. J. Am. Chem. Soc. 2012, 134, 17253.
(2) Suntivich, J.; May, K.J.; Gasteiger, H.A.; Goodenough, J.B.; Shao-Horn, Y. A perovskite Oxide Optimized for Oxygen Evolution Catalysis from Molecular Orbital Principles. Science, 2011, 334, 1383
(3) May, K.J.; Carlton C.E.; Stoerzinger K.A.; Risch, M; Suntivich, J.; Lee, Y.; Grimaud, A.; Shao-Horn, Y. Influence of Oxygen Evolution During Water Oxidation on the Surface of Perovskite Oxide Catalysts. J. Phys. Chem. Lett. 2012, 3, 3264.

Platinum is known to be among the best catalysts for oxygen reduction (ORR), though in recent years researchers have discovered that it binds oxygen too strongly for optimum activity.^[1] Improvements have come by weakening the Pt-O adsorbate binding strength via alloying platinum with other transition metals such as Pt₃Y^[2] and Pt₃Ni.^[3]
In this work, we suggest a strategy of tuning the adsorbate binding strength by tailoring core-shell nanostructures. To do this, two major effects are utilized: the over-weakening of binding for thin shell systems, and the strengthening of binding on undercoordinated sites found commonly on nanoparticles. One monolayer of platinum on ruthenium has been shown to have a much weaker Pt-O bond on the terrace (111) sites. However, by adding additional layers of platinum the effect is lessened and the O-Pt/Ru bond is strengthened.^[4,5] Further significant strengthening of the binding will occur on undercoordinated edge and corner sites which are prevalent in high surface area nanoparticulate catalysts.
Using density functional theory calculations, we identified the Ru@Pt core-shell system as a desirable candidate for an ORR electrocatalyst. To simulate a range of reaction sites that are likely to be present in real nanoparticles, we calculated the Pt-O binding energy on Pt clusters on a Ru substrate for a range of cluster sizes and adsorbate binding sites. The calculations suggest highly active sites on both thin shell corners/edges and thicker shell terraces. This tolerance to particle size and shell thickness is desirable since scalable synthetic methods are unlikely to achieve narrow size/thickness distributions inexpensively.
We have prepared Ru@Pt core-shell nanoparticles utilizing a liquid phase synthesis and characterized them to confirm that the nanoparticles have the intended Ru-core, Pt-shell structure. Rotating disk electrochemistry was used to test catalytic activity and stability. Optimally prepared samples exhibit increased ORR specific activity by a factor of two compared to state of the art TKK platinum catalysts, 0.63 mA/cm²_Pt at 0.9V vs. RHE.^[6] Stability studies (0.6-1.0 V) show a large improvement over the commercial Pt/C control sample. While Pt/C loses about 25% of its mass activity after 10k cycles, Ru@Pt actually gains activity, resulting in a mass activity of 0.28 A/mg_Pt, a 17% improvement over Pt/C.
References:
[1] Noslash;rskov, J. K. et al. The Journal of Physical Chemistry B 108, 17886 (2004)
[2] Greeley, J. et al. Nature Chemistry 1, 552 (2009)
[3] Stamenkovic, V. R. et al. Science 315, 493 (2007)
[4] Lischka, M., et al. Electrochimica Acta 52, 2219 (2007)
[5] Hoster, H. E., et al. ChemPhysChem 11, 1518-24 (2010)
[6] Jackson, A., Viswanathan, V., et al. ChemElectroChem Accepted (2013)

Pt and Pt/C alloy have been most favorable catalysts in oxygen reduction reaction (ORR), which takes place in cathode of proton exchange membrane fuel cell (PEMFC). O2 molecule is adsorbed on Pt and is reduced by combining with protons (H+) and electrons transferred from anode through membrane and outer line, respectively. Even though Pt shows superior activity over all the other materials, it has a couple of disadvantages in price and stability. The price of Pt is high and fluctuates very much depending on time, because it is a noble metal. In addition, the activity of Pt degrades by surrounding molecules like CO and MeOH. Hence, many researches have tried to replace Pt with more cheap and stable material. Among many trial materials, doped carbon-based materials, especially carbon nanotube, have shown comparable activity with Pt.
In this study, Fe & N-doped turbostratic graphite structure is investigated as a catalyst for ORR. We focus on the binding energy of O2 molecule to backbone as well as the bond length between O atoms. They can be indicators for ORR catalysis that binding energy of O2 molecule is much related to activity of ORR and O2 molecule with increased bond length is easy to be dissociated and activated. When we consider only N dopant at first, the calculational results show that O2 molecule prefers to bind to carbon atom in end-on mode and form sp3 bonding. The adsorption process of O2 strongly depends on position and the bond length of adsorbed O2 increases about 8%. If we add Fe atom to previous N-doped structure, Fe not only binds O2 molecule on it, but also enhances binding strength between O2 molecule and neighboring C atom.

Nanoscale Ptminus;Ni bimetallic octahedra with controlled sizes have been actively explored in recent years owing to their outstanding activity for the oxygen reduction reaction (ORR). This presentation will discuss the synthesis of uniform 9 nm Ptminus;Ni octahedra with the use of oleylamine and oleic acid as surfactants and W(CO)₆ as a source of CO that can promote the formation of {111} facets in the presence of Ni. Through the introduction of benzyl ether as a solvent, the coverage of both surfactants on the surface of resultant Ptminus;Ni octahedra was significantly reduced while the octahedral shape was still attained. By further removing the surfactants through acetic acid treatment, we observed a specific activity 51-fold higher than that of the state-of-the-art Pt/C catalyst for the ORR at 0.93 V, together with a record setting mass activity of 3.3 A mg_Pt^-1 at 0.9 V (the highest mass activity reported in the literature was 1.45 A mg_Pt^-1). Our analysis suggests that this great enhancement of ORR activity could be attributed to the presence of a clean, well-preserved (111) surface for the Ptminus;Ni octahedra.

An atomic level fine-tuning of surface reactivity and structural ordering is imperative in enhancing the activity and durability of ORR nanocatalysts for PEMFCs. Alloying Pt with 3d transition metals (typically Fe, Co and Ni) is known to improve the catalytic activity with respect to pure Pt/C, significantly. Particularly in the case of Pt-Fe nanoalloy systems, the structurally disordered bimetallic nanocatalysts were found to be less durable during the lifetime of PEMFCs. As a progression from such disordered systems, we introduce a new class of ordered electrocatalysts amongst Pt-Fe alloys composed of a Pt3Fe2 intermetallic core and Pt-rich shell [1]. These catalysts were found to exhibit an increased mass activity (228%) and an enhanced catalytic activity (155%) for the oxygen reduction reaction (ORR) compared to Pt/C [2]. We have quantified the time-evolution of their structural ordering using an aberration corrected scanning transmission electron microscope. Further, we demonstrate that these catalysts exhibit a static core - dynamic shell (SCDS) regime wherein despite treating over 10,000 cycles, there is negligible decrease (9%) in catalytic activity. The ordered Pt3Fe2 core remained virtually intact while Pt-shell suffered a continuous enrichment. We confirm the existence of SCDC regime by X-ray diffraction and the compositional analyses using energy dispersive spectroscopy. In addition, with an atomic-scale two-dimensional (2-D) surface relaxation mapping, we show that the Pt atoms on the surface are slightly relaxed with respect to bulk. The cycled nanocatalysts were found to exhibit a greater surface relaxation compared to non-cycled catalysts. Finally, with 2-D lattice strain mapping we show that the particle was about -3% strained with respect to pure Pt. While the observed enhancement in their activity is ascribed to such a strained lattice, our findings on the degradation kinetics establish that their extended catalytic durability is attributable to a sustained atomic order.
References:
1. Prabhudev, S.; Bugnet, M.; Bock, C.; Botton, G. ACS Nano 7 6103-6110 (2013)
2. Chen, L.; Chan, M. C. Y.; Nan, F.; Bock, C.; Botton, G. A.; Mercier, P. H. J.; MacDougall, B. R. ChemCatChem 5 1449-1460 (2013)

Fuel cell research in the recent past has witnessed tremendous progress that in addition to holding pivotal scientific relevance also enjoys a conspicuous industrial appreciation. The catalysts design for the ORR in a PEMFC, in particular, is an area that has received momentous thrust as an effect. Platinum, although is known to exhibit exceptional activity towards the sluggish ORR kinetics, still remains an economically nonviable option owing to its exceedingly high costs. Currently, there exists a clear agreement in the literature that nanoscale alloying of Pt with 3d transition metals, in addition to reducing the mass loading of Pt, also enhances the catalytic activity towards the ORR. Also, the ordered nanoalloys exhibit an extended catalytic durability over their disordered counterparts. Furthermore, the ORR reactivity of such ordered intermetallic alloys could be fine-tuned through a selective enrichment of the nanoparticle surface with Pt atoms. The nanoparticles so designed to comprise a Pt-rich shell encompassing an ordered intermetallic core, form a new class of ORR electrocatalysts termed the intermetallic core-shells (IMCSs), and have recently been found to exhibit an exceptional catalytic activity and enhanced durability in the case of Pt-(Fe [1] and Co [2]) systems.
In the light of these recent observations, we believe that the atomic-ordering and a preferential segregation of Pt are the two integral factors that dictate the overall performance of a nanocatalyst design. One principal segment of our current work has been to understand the ordered transformation and segregation kinetics in Pt-Fe nanoparticles. The as-received particles that existed as disordered systems were annealed at 200-300-400-500-600-700-800 degC. These heat-treated nanoparticles were characterized using a sub-angstrom resolution aberration corrected STEM. In addition to STEM-HAADF imaging, we have also utilized the capabilities offered by EEL spectroscopy for obtaining chemical maps down to atomic-scale. We confirm that Pt is not the only participant in the segregation process but is to be contending with Fe. Deploying the Z-dependence of STEM-HAADF contrast we have been able to track the disorder-to-order transition at an atomic resolution. We show that the ordering starts at relatively low temperature at the core, and based on its initial composition and size the particles evolve into an ordered nanoalloy with segregated Pt and Fe shells. Finally, our work provides new insights into the voltammetric dealloying mechanism by collecting a statistically significant set of EELS chemical maps before and after dealloying. In summary, we track the evolution of Pt-Fe IMCS nanoparticles at the atomic-scale, from synthesis to a functional electrocatalysis.

References
1. Prabhudev, S et.al. ACS Nano 2013, 7, 6103-6110
2. Wang, D et.al. Nature Materials 2012, 11, 1-7

Derivatization of poly(benzimidazole) (PBI) with methyl groups generates poly(dimethylbenzimidazolium) (PDMBI), an anion exchange material. By using a simple ion exchange process, it is possible to produce PDMI salts with a variety of counter-ions. Anionic conductivity for the PDMI membranes was found to be surprisingly high even though the membranes generally exhibit very low water uptakes. Using the concept of steric crowding around the C2-benzimidazolium PDMBI analogues were prepared that were stable in KOH solution. The hydroxide-conductivity of these materials is reported.

The proton exchange membrane (PEM) fuel cell when using hydrogen as the fuel has a very high power density and is attractive for the automotive industry. . Anion exchange membrane (AEM) fuel cells could potentially use non-precious metals on both anode and cathode and should be much more fuel flexible than PEM fuel cells. We have been building AEM fuel cells based on a cationic polyphenylene polymer developed at Sandia National laboratories. I will first briefly share our experiences with this polymer and various catalysts supplied from our partners. Recently this has been modified with novel cations that allow adequate membrane stability to optimize the AEM fuel cells we are building, and recent results are quite encouraging.
The development of the AEM fuel cell is still very much a polymer problem, robust AEMs must be developed, and AEMs must be tailored specifically for the anode and cathode of the fuel cell. We have been using a ground up approach to develop new AEMs. Using di-block polymers of well-defined geometry we are exploring how fast anion transport may be achieved in AEMs. Using a wide variety of techniques it seems that a water wire is highly implied in materials that exhibit practical hydroxide conductivities. The dimensions of this are verified by small angle neutron scattering work. As a screening tool we are studying materials with fluoride counter ions. This overcomes the issues associated with hydroxide experimentation (cation degradation, reaction with atmospheric CO2) and calaculation ( recative models can take >30 days on a modern super-computer). Such studies vastly increase the speed at which an AEM can be experimentally characterized and described computationally. This allows us to more rapidly screen structures for fast anion conductivities before investing in comprehensive studies of the reactive hydroxyl anion in AEMs that may not be robust enough to survive ion exchange with base.
We have recently designed a standard test for AEM stability, which is designed to both understand the mechanism of AEM degradation and to serve as a criterion for when an AEM should be selected as promising for further study. An increasing amount of our work is in film processing. As anion transport will always be slower than proton transport, it will be necessary to utilize AEMs as thin robust films. Many AEMs are intrinsically brittle; we are developing methods to form films from these materials, while understanding the polymer science.
In this talk I will give an update of efforts to make thin robust AEMs with fast anion transport and promising stability for fuel cell applications.
This work was supported by the Army Research Office under the MURI program by agreement W911NF-10-1-0520.

Alkaline anion exchange membranes with varying side-chain chemistries have been investigated as part of ongoing studies of APEMFCs. Membranes (denoted RG) are formed following post-electron-beam-irradiation graft copolymerisation of precursor polymer films, via reaction with vinyl benzyl chloride and subsequent introduction of a range of quaternised nitrogen centres as tethered cationic head groups. Head group stability under alkaline conditions has been probed in depth, over extended periods in elevated temperature ex situ studies and using subsequent titrimetry (determining variations in IEC), 13C NMR spectroscopy and Raman spectroscopy. A new ionomer approach has resulted from using a similar copolymerisation + functionalization treatment of precursor polymer powders; the performance in H2/O2 APEMFCs of MEAs containing such an ionomer is significantly enhanced relative to use of earlier electrode architectures.
Similar anion exchange membranes have been tested along with other related membranes, with a view to application in redox flow batteries, starting from ETFE and HDPE parent films. Their stability to oxidation in vanadium redox electrolyte (V(+5) in aqueous sulfuric acid) has been examined in accelerated (elevated temperature) tests, with that stability examined via determined electrolyte reduction, remaining IEC, changed ionic conductivity, Raman spectroscopy and 13C NMR spectroscopy. RG membranes survived this testing intact, whereas other membranes often disintegrated. Additionally, all membranes were studied for their permeability to aqueous vanadium species, with permeabilities being highest for V(+4); a simple cell with spectroscopic determination of vanadium was developed and validated. Permeabilities were lowest for less hydrophilic membranes (and then substantially less than that of Nafion), suggesting that these would have the least vanadium crossover (which constitutes a parasitic loss) in an all vanadium redox flow battery (VRFB).
Acknowledgement The programs at the University of Surrey in energy materials and in energy generation and storage devices are funded by the Engineering and Physical Sciences Research Council of the United Kingdom.

A series of three membrane types has been screened for medium temperature solid polymer electrolyte water electrolysis in membrane electrode assemblies coated with 2 mg cm-2 of iridium oxide as a catalyst for the oxygen evolution reaction, synthesized via a hydrolysis method from the chloride precursor, and deposited on the membrane either directly by spray deposition or by decal transfer. The short-side-chain perfluorosulfonic acid Aquivion® ionomer of equivalent weight 870 meq g-1, in membranes of thickness 120 µm, gives higher water electrolysis performance at 120 °C than a composite membrane of Aquivion® with zirconium phosphate, while a sulfonated ether-linked polybenzimidazole, sulfonated poly-[(1-(4,4&’-diphenylether)-5-oxybenzimidazole)-benzimidazole], shows promising performance and no transport limitations up to 2 A cm-2. The lowest cell voltage was observed at 120 °C for an MEA prepared using spray-coating directly on the Aquivion® membrane, 1.57 V at 1 A cm-2.
The research leading to these results has received funding from the European Community&’s Seventh Framework Programme (FP7/2010-2013) for the Fuel Cells and Hydrogen Joint Undertaking under grant agreement Electrohypem no. 300081.

Alkaline anion-exchange membranes (AAEMs) for solid alkaline fuel cells (SAFC) application were successfully prepared by radiation induced grafting of Vinyl benzyl chloride onto ultra-high molecular weight polyethylene powder (UHMWPE), followed by film fabrication by melt pressing and quaternization with a Guanidine derivative, 1,1,3,3-tetramethyl-2-n-butylguanidine (BTMG). The chemical structures of the resulting AAEMs were examined by Fourier transform infrared, which showed that the grafted membranes were successfully functionalized by modified guanidine. The performance of the AEMs, including ion exchange capacity, water uptake, in-plane swelling, methanol uptake, methanol permeability, and hydroxide ion conductivity were investigated. Thermal analysis showed that the Guanidine-based AAEMs comprises better thermal stability. The AAEMs membrane exhibited a maximum ionic conductivity of 32.7 mS cmminus;1 at 90 °C. Methanol permeability is found to be in the order of 10minus;9 cm2 s-1, which is significantly lower than that of Nafion®. The membranes have useful properties consistent with anion exchange membranes suitable for alkaline fuel cells.

H2O2 is a chemical with a worldwide production of 3 M tons / year, used mainly in the paper and chemical industry (1). Currently, H2O2 is primarily produced via the anthraquinone process, a batch synthesis method conducted in large scale facilities. While the inherent inefficiency of batch synthesis methods has motivated researchers toward developing a direct synthesis route, progress to date has been scarce due to the lack of efficient catalysts. We and others have recently proposed an electrochemical route where H2O2 can be synthetized by reducing oxygen in fuel cells or electrolyzers (2,3,4). We developed a theoretical framework for the targeted discovery of electrocatalysts for this reaction based on the isolated active site concept. This led to the discovery of Pt-Hg as an active, selective and stable material. Now, we have extended the search to other electrocatalysts. By combining electrochemical experiments and density functional theory calculations we study the trends in activity and selectivity on various materials. We propose a model where the oxophylicity of the catalyst sets its activity, while selectivity is determined by dissociation of the O-O bond. In particular, Pd-Hg catalysts present a record high activity, with Pd-Hg/C nanoparticles showing a five-fold improvement in mass activity (i.e. A/mg precious metal) over the best performing catalysts in the literature.
1 Campos-Martin, J. M., Blanco-Brieva, G. & Fierro, J. L. G. Hydrogen Peroxide Synthesis: An Outlook beyond the Anthraquinone Process. Angewandte Chemie International Edition 45, 6962-6984, doi:10.1002/anie.200503779 (2006).
2 Jirkovský, J. S. et al. Single Atom Hot-Spots at Au-Pd Nanoalloys for Electrocatalytic H2O2 Production. Journal of the American Chemical Society 133, 19432-19441, doi:10.1021/ja206477z (2011).
3 Fellinger, T.-P., Hasché, F., Strasser, P. & Antonietti, M. Mesoporous Nitrogen-Doped Carbon for the Electrocatalytic Synthesis of Hydrogen Peroxide. Journal of the American Chemical Society 134, 4072-4075, doi:10.1021/ja300038p (2012).
4 Siahrostami, S., Verdaguer-Casadevall, A., Karamad, M., Deiana, D., Malacrida, P, Wickman, B., Escudero-Escribano, M., Paoli, E. A., Frydendal, R., Hansen, T., Chorkendorff, I., Stephens, I, Rossmeisl, J., Nature Materials, 2013, in press DOI: 10.1038/NMAT3795.

Microbial electrochemical cells (MECs) show great potential for energy recovery from dilute reservoirs of organic matter, such as domestic wastewater, marine sediment, waste biomass and methane hydrate. In order to enhance the performance of the MECs, my study focuses on applying materials science and nanotechnology to develop new MEC electrodes and configurations.
In the first part of this talk, a three-dimensional (3D) microbial bio-electrode design will be proposed. The 3D bio-electrode is realized by conformally coating carbon nanotubes (CNTs) or graphene on a macroscale porous substrate, such as textile or sponge. Such composite bio-electrodes provide a two-scale porous structure, a macroscale porous textile or sponge providing an open 3D space accessible for microbial growth and a microscale porous CNT or graphene layer showing strong interactions with the microbial biofilms. Compared with a widely used commercial carbon cloth anode, our composite bio-electrodes achieve significantly improved performance. At the same time, the capital cost is at least one order of magnitude less.
In the second part, a new MEC, referred as a “microbial battery (MB)”, will be introduced. The key difference of MBs to MFCs is the use of solid-state cathodes to replace the oxygen gas cathodes. The MBs overcome the major drawbacks of MFCs: voltage losses at oxygen cathodes and introduction of oxygen into the anode compartment. A bench-scale MB with silver-oxide as the solid-state electrode achieves an efficiency of electrical energy conversion of 49% based on the combustion enthalpy of the organic matter consumed or 44% based on the organic matter added. Electrochemical re-oxidation of the solid-state electrode decreases net efficiency to about 30%, but this (un-optimized) net efficiency is still about an order of magnitude higher than the energy recovery efficiencies achieved with MFCs.

Deoxyribonucleic acid (DNA) has unique molecular recognition and self-assembly capabilities derived from its complementary base pairs. The use of DNA to build nanostructured materials has attracted a growing number of researchers.[1,2] With DNA as the assistant assembly component, we have also built several nanostructured materials with unique properties for high-performance supercapacitor, lithium-ion battery or electrocatalysts. For instance, we developed a DNA-assisted assembly approach to fabricate a capacitor-type electrode material, DNA-functionalized carbon nanotubes (DNA@CNTs), and a battery-type electrode material, DNA@CNTs-bridged MnO2 nanospheres, for asymmetric supercapacitors. A high energy density of 11.6 Wh kg-1 was achieved at a power density of 185.5 W kg-1 with a MnO2 mass loading as high as 4.2 mg cm-2.[3] Through its PO43- groups regularly arranged on the sugar-phosphate backbone, we used DNA to direct the growth of a network structure of ultra-small FePO4 nanoparticles on double-wall carbon nanotubes. These nanoparticles as cathode materials in lithium-ion batteries exhibited nearly 100% theoretical storage capacity for FePO4 active component.[4] We also utilized DNA to functionalize graphene and to further guide the growth of ultrasmall palladium (Pd) nanocrystals with uniform distribution on graphene and demonstrating considerably improved electrocatalytic performance towards formic acid oxidation for direct formic acid fuel cells.[5] It is expected that the DNA-assisted assembly approach can be extended to fabricate other kinds of functional materials with desired properties for a broad range of applications in energy conversion/storage systems, catalysts and optoelectronic devices.
Referneces and notes
[1] E. Auyeung, J. I. Cutler, R. J. Macfarlane, M. R. Jones, J. Wu, G. Liu, K. Zhang, K. D. Osberg, C. A. Mirkin, Nat. Nanotechnol. 2012, 7, 24-28.
[2] A. V. Pinheiro, D. Han, W. M. Shih, H. Yan, Nat. Nanotechnol. 2011, 6, 763-772.
[3] C. X. Guo, X. M. Lu, Submitted, 2013.
[4] C. X. Guo, Y. Q. Shen, Z. L. Dong, X. D. Chen, X. W. Lou, C. M. Li, Energy Environ. Sci. 2012, 5, 6919-6922.
[5] C. X. Guo, L. Y. Zhang, J. W. Miao, J. T. Zhang, C. M. Li, Adv. Energy Mater. 2013, 3, 167-171.

Miniaturized enzymatic biofuel cells (EBFCs) converting biological energy into electrical energy by using enzyme-modified electrodes are considered as a candidate to power the implantable medical devices and portable electronics. However, insufficient cell lifetime and low power density are two big obstacles to be overcome before miniaturized EBFCs become competitive in the practical application. Utilizing the high surface area materials as the electrode could be one of the effective solutions. Recently, nanomaterials such as carbon nanotubes (CNTs) and graphene have attracted great attention and emerged as a promising electrode material towards biofuel cell applications due to their interesting physicochemical properties.
Therefore, in this study we present an EBFC design employing 3D C-MEMS micropillar arrays integrated with graphene/CNT composite. Electrostatic spray deposition (ESD) will be used to deposit graphene/CNT onto the micropillar arrays to further increase the surface area. Next, the CNT/graphene modified electrode surface will be functionalized with amino group to form covalent bonding with enzyme. Glucose oxidase and laccase will be immobilized on the anode and cathode, respectively. The output potential and power density of the EBFC will be evaluated. The effort on fabricating the graphene/CNT based 3D electrodes, developing reliable covalent enzyme immobilization as well as obtaining improved EBFC performance will be presented in this talk.

One possible solution to the world&’s growing energy problem is to improve the efficiency of energy conversion processes by harnessing their waste heat. At present, 70 % of the energy generated in cars is dissipated into the environment through hot exhaust pipes and brakes. Even the most efficient internal combustion engines only operate at ~50 % efficiency, with the remainder ending up as waste heat. Thermogalvanic systems, also known as thermocells, are simple devices that allow direct transduction of thermal to electrical energy. Thermocells are comprised of two electrodes held in contact with a redox based electrolyte. Exposure of the two half cells to a temperature gradient creates a potential difference so that power can be extracted from the cell. Initial research on thermocells focused on platinum electrodes, the archetypal non-reactive catalytic material. In order to make thermocells commercially viable, the electrode material needs to be replaced such that the price per Watt is minimized and an efficiency between 2-5 %, relative to a Carnot engine, is attained. Developments in the field of carbon nanomaterials reveal that their Nernstian behavior and fast electron transfer kinetics make them ideal electrode materials. Initial studies on single walled carbon nanotubes (SWNT) and reduced graphene oxide (rGO) as electrodes for thermocells yield promising results owing to their porous nature resulting in a higher electroactive area. However, ion accessibility must also be considered. To ensure continuous generation of power in a thermocell, reaction products formed at one half-cell must be transported to the opposite side. This mass transport problem is exacerbated in pure CNT and rGO electrodes owing to the tortuous nature of the former and sheet restacking in the latter. In this study we show that by controlling the composition and thickness of SWNT-rGO composite electrodes we are able to attain a balance in porosity and tortuosity; i.e. increase the electroactive area while allowing rapid ion movement in the thermocell. Through the use of a novel stacked electrode configuration (10 alternating layers of the optimised SWNT-rGO film and stainless steel mesh), we attain ~380 % and ~280 % improvements in normalized areal power density (P_area/ΔT² = 1.9 mW/m²-K²) and normalized mass power density (P_mass/ΔT² = 49 mW/kg-K²), respectively as compared to previous work. These results demonstrate enhanced thermocell performance using significantly less active material; i.e. lower price per Watt. Through the use of these novel electrodes a power conversion efficiency relative to a Carnot engine (Phi;_r) of 2.63 % was attained. This Phi;_r is a remarkable 88 % improvement compared to the highest reported Phi;_r in thermocells (1.4 %) and within the range for commercial viability of these devices (i.e. Phi;_r between 2 to 5 %).

A millimeter planar polymer light-emitting electrochemical cell was turned on in a cryogenic probe station and subsequently cooled to freeze the doping profile. A 442 nm laser beam guided by an optical fiber was scanned across the interelectrode gap of several millimeters and the photovoltaic response was measured as a function of position. Both photocurrent and photovoltage profiles display a prominent peak at the geometric boundary of the p- and n-doped regions. A non-zero photovoltaic response throughout the p- and ndoped regions can be explained by various broadening mechanisms including non-uniform doping and secondary excitation by waveguided light. The photovoltaic response is weakest at the electrode/polymer interfaces.

Organic radical batteries (ORBs) comprise a novel technology that uses cathodes based on stable organic radical-based polymers. Polymeric organic nitroxide radical materials, such as 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), have received great interest for various energy storage applications. These materials are readily synthesized from environmentally benign precursors, and TEMPO in particular has been shown to have very fast charge transfer kinetics. These types of materials show great promise as cathode materials because the neutral, radical species are remarkably stable, and the one-electron oxidation is fully reversible.
In order to guide the development of new organic radical electrode materials and to aid in the design of improved electrode structures, a detailed understanding of the fundamental mechanisms involved in electronic charge transfer and anion interfacial mobility in the polymer matrix is required. The work reported here has focused on ab initio electronic structure calculations and large-scale molecular dynamics (MD) simulations to predict charge transport in organic radical films. These theoretical predictions are compared to AC impedance experimental measurements to establish a detailed understanding of the fundamental mechanisms involved in electronic charge transfer and ionic motion within the TEMPO matrix. Electronic structure calculations were conducted on subunits of interest to relate oxidation states to in situ spectroscopic monitoring of oxidation and ion pairing.
Polymeric TEMPO morphologies have been generated using atomistic MD simulations with force fields we have adapted to treat radicals for neutral and ionic systems generated during charge/discharge of the test cells. Morphological features dictated by polymer structural properties, including nitroxide radical density and molecular anion type, have been correlated with experimental results, and multiple iterative modifications of the theory-experiment results have been completed. We will describe the implications of these simulations to understanding barriers to charge migration and transport in stable, radical-containing polymeric films.

Hybrid graphene materials have been widely researched for electrochemical energy conversion
devices. Existing schemes for combining graphene-like supports with various nanostructured materials usually rely on harsh chemistry and fail to maintain graphene&’s pristine features or achieve high-quality interfaces.
We demonstrate epitaxial-like growth of catalyst nanocrystals and thin films using mild, industry-compatible processes that chemically activate graphene and result in high-quality, atomically sharp interfaces. The resulting hybrid structures are expected to find applications as fuel cell and photoelectrochemical electrodes. In particular, we highlight graphene-Pt and graphene-TiO2 structures as candidate electrodes for fuel cells and water-splitting electrochemical devices.
We use plasma reactions to mildly functionalize graphene surfaces and then grow nanocrystals and thin films, such as Pt and dielectrics, from the gas phase. We characterize the resulting hybrid structures with AFM, SEM, aberration-corrected HRTEM and STEM, and observe that the growth characteristics depend on functionalization level, graphene layer thickness and growth temperature. We demonstrate that the graphene support influences the crystallographic orientation of the nanocrystals, and that the growth is epitaxial-like in character. We characterize the basic electrochemical performance of graphene-Pt structures.
This work has important implications for the rational bottom-up fabrication of graphene-based energy conversion devices. The ability to tailor the chemistry and hierarchically build vertical graphene heterostructures with nanocrystals and thin films will provide these devices with capabilities previously out of reach for graphene.

The catalytic activity of early transition metal carbides, including their catalytic and mechanistic properties in various catalytic reactions, has been actively studied since tungsten carbides were first found to display platinum-like behaviour. Previous reports have demonstrated that cost-effective tungsten carbide (WC)-based materials efficiently catalyze various reactions that require precious metal catalysts, including methane reformation, desulfurization, hydrogen evolution reaction (HER), and ammonia decomposition. Although progress has been made in improving catalytic performance, WC-based materials still have markedly lower catalytic activity and stability compared to noble metal catalysts in most experimental systems.
In the present work, we developed a facile approach for the preparation of well-controlled tungsten carbonitride nanoparticles that possess the following desirable characteristics: (1) uniform, small-sized nanoparticles, (2) nitrogen-rich backbones, and (3) pure tungsten carbonitride crystal structure. For the synthesis, polydiaminopyridine (PDAP) was first synthesized from the nitrogen-rich (N-rich) monomer diaminopyridine in the presence of Na2WO4. Protons released during the PDAP polymerization process reacted with soluble Na2WO4, resulting in the in-situ formation of hybrid nanomaterials composed of PDAP and insoluble H2WO4 nanoparticles. This unique synthesis approach not only allows nano-hybrids of H2WO4/PDAP polymer to be fabricated in a single step, but also supports the coordination of W species due to the high density of N sources from PDAP. The Fe-WCN materials were characterized as a model electrocatalyst for HER, and it displays efficient HER activities in both acidic and alkaline media, with an HER overpotential of ~100 mV and a tafel slope of ~47 mV dec-1 in acidic medium (pH 1), which is much better than that of tungsten carbonitride materials synthesized by traditional nitridation method.

Research on the electrochemical reduction of CO₂ has focused on the gathering of fundamental understanding of the catalytic process through investigations on a range of transition metals. Carbon monoxide is believed to be a key intermediate and the CO binding energy (E_B[CO]) of the transition metal catalyst determines its activity for carbon dioxide reduction reaction (CO₂RR). We investigated CO₂ electroreduction on silver-catalyzed systems for two main reasons: (1) silver has high activity for CO₂RR to CO, and (2) it has a late onset for hydrogen evolution, an unwanted byproduct of electrochemical reduction in an aqueous environment. Silver is known to have a weak, sub-optimal E_B[CO]; by exploring ways to increase the E_B[CO] of silver, a higher activity of the CO₂RR may be attained, confirming the significance of the CO intermediate species.
Initial investigations using a polycrystalline silver surface were performed in a custom electrochemical cell, which offers high sensitivity for minor products of CO₂RR. As expected from literature, CO and H₂ were observed as major products, along with formate as a minor product. In addition to these products, methane, methanol, and ethanol were also detected as minor products at high overpotentials, illustrating the ability of silver to produce hydrocarbon/oxygenate products even with its weak E_B[CO]. Two surface modification schemes, nanostructuring and alloying, were implemented in order to shift the E_B[CO] of the catalyst surface. Enhancement in CO₂RR activity was observed for the nanostructured surfaces, while changes in the selectivity amongst the minor products were observed for the alloyed surfaces. Shift in the E_B[CO], increase in the surface area, and effects of alloying are incorporated in the analysis for the explanation of these observations.

Developing an effective electrocatalyst in oxygen evolution reaction (OER) plays a critical role to many energy conversion and storage processes, such as metal-air batteries and water splitting. Recently, transition metal-based oxides[1] and hydroxides[2] have been reported to have high activity and stability for OER in alkaline media. Despite recent advances in the development of catalysts to negotiate the OER, it is still a topic of ongoing interest because of the increasing demand for energy storage and conversion from alternative energy sources. Herein, we report the synthesis of reduced graphene oxide intercalated nickel-iron layered double hydroxide (NiFe-rGO LDH). Intercalation of graphene oxide into NiFe LDH by ion exchange resulted in the formation of NiFe-GO LDH that was further reduced to NiFe-rGO. The high activity for OER of crystalline NiFe LDH nanosheets and enhanced electron transport resulted from the intercalated rGO led to the superior OER properties of as synthesized NiFe-rGO LDH, which comparable to those of commercial noble metal catalysts.

Figure 1. (a) SEM image of FeNi-GO LDH and (b) polarization curves of FeNi-GO LDH, and various FeNi LDH and GO complexes in 1 M KOH.

[1]: R. D. L. Smith, M. S. Prevot, R. D. Fagan, Z. Zhang, P. A. Sedach, M. K. J. Siu, S. Trudel, C. P. Berlinguette, Science, 2013, 340, 60-63.
[2]: M. Gong, Y. Li, H. Wang, Y. Liang, J. Z. Wu, J. Zhou, J. Wang, T. Regier, F. Wei, H. Dai, J. Am. Chem. Soc. 2013, 135, 8452-8455.

Solar-water-splitting is a promising alternative to conventional energy systems, though the significant kinetic overpotential of the oxygen evolution half-reaction (OER) requires the use of an inexpensive yet efficient catalyst. OER catalysts commonly undergo significant chemical and structural changes from the bulk material when employed in electrochemical cells and identifying catalytically active species remains a key challenge. Our current research focuses on tracking changes to common Ni-based OER materials at the catalyst-solution interface to identify the catalytically active surface species and determine how these species differ from bulk species.
The highest activity catalysts are transition-metal based oxide materials. It was been shown that the incorporation of small amounts of Fe into NiOX, Ni(OH)2/NiOOH thin film catalysts significantly increases the catalytic activity of the material. We study the incorporation of Fe impurities and surface reconstructions of several previously reported transition metal-oxide OER catalysts including LaNiO3, NiCo2O4, and Ni-borate. To test the hypothesis that common Ni-based anode materials convert to NiOOH phases, absorb Fe from solution, and thus are all likely very similar under OER conditions we use cyclic voltammetry, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) to track changes at the catalyst surface. We find that Fe integration occurs during electrochemical cycling in alkaline media and to larger degree during conditioning at anodic potentials. Fe incorporation is evident in XPS spectra, exhibiting a 2-3 times increase in Fe concentration in catalyst films after conditioning.
Further evidence for the conversion to Ni(OH)2/NiOOH and Fe incorporation is found in the shifting of Ni redox peaks and significant improvement in OER catalytic activity in cyclic voltammograms. X-ray diffraction shows that the bulk of material remains as deposited, suggesting that many previous reports of Ni-based OER catalysts may be influenced by the presence of an amorphous Fe-containing surface species. Furthermore, the increase in Ni peak area indicates that conditioning also affects the number of Ni accessible to solution and therefore water oxidation.

Ongoing experiments use TEM to directly image the surface species and investigate the interface of the catalytically active surface and the bulk crystalline film. Additionally, XPS depth profiling is underway to quantify the incorporation depth and concentration profile of Fe impurities. These detailed surface studies have significant implications for the interpretation of electrocatalysis data from inorganic oxides as well as for the solid-state design of OER catalysts.

Realizing the potential of anion-exchange-membrane unitized regenerative fuel-cells (AEM-URFCs) to provide scalable and cost-effective storage for renewable energy requires improved catalysts for the hydrogen oxidation and evolution reactions in basic conditions. Using a theory-guided approach, we have synthesized NiAg alloys and found them to be promising candidates for these reactions. Because silver and nickel are thermodynamically insoluble, we employ a vapor-deposition synthetic approach. Electrochemical testing demonstrates that the hydrogen evolution activity of the most active catalyst, Ni$_{0.75}$Ag$_{0.25}$, is approximately twice that of pure nickel, and the stability and hydrogen oxidation activity are both comparable.

Studies on the electrochemical reduction of CO2 at metallic electrodes have suggested that the adsorption of hydrogen species is structure-sensitive and surface roughening is likely to introduce defects favorable for reaction of adsorbed hydrogen atoms, which is an important step in the reduction of CO2 in protic media. To further gauge this effect, copper foam electrodes on copper substrates were prepared by a simple electrodeposition process following reported literature methods.
Electrolysis was performed in a typical H-cell under potentiostatic conditions. The microporous foams were mechanically stable such that the structure was intact during preparation, handling and electrolysis. The faradaic efficiency of formate obtained from the reduction of CO2 at a bare copper electrode and the copper foam electrode were found to be significantly different.XRD analysis revealed no major differences from a high purity planar copper substrate. The hierarchical porous architecture with high surface area and pore volume could be beneficial for the unimpeded mobility of reactants and products contributing to the observed enhancement in efficiency; viewed as being more physical than chemical catalysis. The 3D structure of the foam allows for superior interaction between the reactant, electrode and electrons in three-dimensional space instead of being confined to a two-dimensional planar electrode. The effect of varying pore size of the metal foam electrode will be discussed.

Electrochemical reduction of carbon dioxide (CO2) is an important technology for conversion from electricity to organic energy source. That has been attracting broad interest of researchers for decades, and some of transition metals were found to reduce CO2 to carbon monoxide and/or organic materials. Among them, copper (Cu) electrode is famous for producing hydrocarbons and alcohols, which can be directly used for fuels. However, the component is a mixture of major and minor products, which means a poor selectivity of hydrocarbons and alcohols.
In the electrochemical CO2 reduction, there are many parameters that affect the selectivity of products; kind of electrode, voltage, current density, electrolyte, pressure of CO2, temperature, etc. To control the selectivity, it is necessary to know the synergetic effect of these parameters on CO2 reduction reaction. Although some researches report an effect of a single parameter, synergetic effects of these parameters have not been fully investigated.
For the systematic investigation of the effects of parameters, we introduce a new combinatorial electrochemical screening system. We developed a system which can conduct 8 parallel experiments automatically, with precisely controlling the parameters including pressure and temperature. With combinatorial screening system, one can easily obtain a map of synergetic effects of parameters which can be used for controlling selectivity of CO2 reduction.
It has been already known that increasing current density at Cu cathode makes the hydrogen generation dominant with suppressing the CO2 reduction. The suppressed CO2 reduction is reported to be magnified at highly pressurized state, such as over 10 atm of CO2. In the present study, our systematic mapping of the relation between current density and CO2 pressure shows that the reaction products are significantly changed even in a relatively low pressure (~ 5 atm) of CO2. The distribution of the reaction products changes continuously and drastically in the current-pressure mapping. Several experiments tell us a whole tendency of the distribution and optimized reaction condition for the production of a desired product. Thus, the combinatorial screening system can be a powerful tool to construct an optimized chemical reaction by investigating the synergetic effects of these parameters.

Global dependence on fossil fuels as energy sources and the alarming increase of greenhouse gas emissions has necessitated the development of carbon-free and carbon-neutral renewable energy sources for the future. The sequestration of CO₂ emissions and the subsequent electrochemical reduction of CO₂ into fuel products, forms a carbon-neutral synthetic fuel cycle which could potentially be streamlined into existing fuel infrastructures. To date, only Cu has displayed any propensity as a catalyst to electrochemically reduce CO₂ into longer chain hydrocarbons, carboxylates, and alcohols. However, Cu generally requires a large overpotential to reduce CO₂ and has little product selectivity as a catalyst. Recent theoretical work indicates that scaling relations associated with reaction adsorbate binding energies could be limiting the CO₂ reduction activity of transition metal catalysts.¹ These studies suggest that alloying can improve the activity and selectivity of a CO₂ reduction catalyst by decoupling the binding energies of specific reaction intermediates. Here, we investigate the use of physical vapor deposition (PVD) to synthesize a targeted library of binary alloy thin films for CO₂ reduction. X-ray diffraction and x-ray photoelectron spectroscopy characterization of alloy thin films confirm that the bulk and surface composition, respectively, can be rationally tuned with source deposition rates. These results demonstrate the compatibility and "plug and play" utility of PVD for the synthesis of a library of alloys. The CO₂ reduction activity and selectivity of PVD alloys were examined using electrochemical measurements in tandem with gas phase (gas chromatography) and liquid phase (nuclear magnetic resonance) product detection methods.
¹ Peterson, A.A.; Noslash;rskov, J.K., "Activity Descriptors for CO₂ Electroreduction to Methane on Transition-Metal Catalysts," J. Phys. Chem. Lett., 2012, 3, 251-258.

Metals employed as electrocatalysts are generally of nanoscale dimensions, presenting ensembles of coordinatively unsaturated atoms at their surface. Coordinatively unsaturated atoms which come into contact between neighboring nanoparticles react to form metal-metal bonds, reducing the number of surface sites available for catalysis. Nanoscale electrocatalysts are frequently dispersed on a support to minimize contact between particles. However, the surface of an electrode is a dynamic environment involving moving interfaces between solids, liquids, and gases, at which nanoparticles can migrate along the support and collide with each other, bringing coordinatively unsaturated sites into contact. To limit the extent to which coordinatively unsaturated sites react to form metal-metal bonds, these sites may be thermodynamically stabilized by organic or inorganic species which assist in maintaining a high surface area morphology. Thermodynamic stabilization is challenging because it often comes at the expense of attenuating catalyst activity due to poisoning or blocking of catalytic sites. We report a combination of electrochemical conditions and ligands which drive gold nanoparticles to assemble into dendritic structures which are active for CO2 reduction. This stabilization strategy allows for preserving the high surface area of the catalyst while avoiding poisoning of catalytic sites for reductive chemistry. Monte Carlo simulations reveal the mechanism by which the dendrites form and detailed electrochemical studies highlight the role of the ligand in driving dendrite formation.

We have studied the electrochemical reduction of CO₂ using Cu₂O nanoparticles deposited on planar electrodes. Nanoparticles are prepared in aqueous solution by chemical reduction of CuCl₂ using ascorbic acid with polyethylene glycol surfactant. The particles are then re-suspended in ethanol with added Nafion binder and brush-coated onto glassy carbon substrates.

The CO₂ electroreduction activity is measured in KHCO₃ electrolyte under flowing CO₂ using a two-compartment electrochemical cell. Product formation rates are determined using gas chromatography; major gas phase products include CO, H₂, C₂H₄, and CH₄, while liquid phase products include C₂H₅OH and 1-C₃H₅OH.

The observed product distribution agrees with results obtained previously using similar Cu₂O particles deposited on carbon fiber paper supports, as well as Cu₂O catalysts prepared by electrodeposition or thermal oxidation. In particular, the catalysts produce a much higher ratio of C₂H₄ to CH₄ than observed using poly-crystalline Cu foil. The potential dependence of the formation rates for hydrocarbon and alcohol products is roughly two times greater than for H₂ and CO formation.

Both XRD and SEM measurements confirm the Cu₂O nanoparticles undergo reduction to Cu metal under CO₂ reduction conditions, accompanied by significant morphological changes. Thus the kinetic results are consistent with current models that the increased C₂H₄/CH₄ ratio is due to the presence of a more open atomic structure on the freshly reduced Cu surfaces, relative to the low-index Cu(111) surface that is dominant on polycrystalline Cu foils. We propose a qualitative framework based on a dual-site mechanism that can account for the observed product selectivities.