Thomas J. Schmidt, Paul Scherrer Institut
Vojislav Stamenkovic, Argonne National Laboratory
Matthias Arenz, University of Copenhagen
Shigenori Mitsushima, Yokohama National University
Symposium Support Nissan Research Center
Monday PM, November 26, 2012
Hynes, Level 3, Room 304
2:45 AM - C3.01
Comparative Study of the Solid Electrolyte Interphase on Graphite in Li-ion Battery Cells Using XPS, TOF-SIMS, and Electron Microscopy
Jung Tae Lee 1 Naoki Nitta 1 Jim Benson 1 Thomas Fuller 2 Gleb Yushin 1
1Georgia Institute of Technology Atlanta USA2Georgia Institute of Technology Atlanta USAShow Abstract
Graphite is the most commonly used anode material for commercial lithium ion batteries and has been very well studied. The excellent properties of graphite are due primarily to the robust solid electrolyte interphase (SEI). Consequently, numerous studies have been conducted to study these properties utilizing various techniques. Many of these techniques such as EDS, XRD, and TGA, are unable to resolve subtle changes in these thin SEI films due to their large information depths. [1,2] Due to these problems analyses using high spatial resolution have been applied using XPS and TOF-SIMS to observe the chemical and concentration gradients of these complex SEI films on the nanometer scale and as a function of their cycle life. This research analyzed commercially available electrodes composed of a graphite anode, nickel manganese oxide cathode, and PC:EC:DEC 1:1:3 with LiPF6 electrolyte at three stages of cycling. Cell 1 experienced only formation process to form a protective solid electrolyte interface film on the surface of graphite electrode. Cell 2 stored 14 days at 10 % of state of charge (SOC) at 25°C and then 700 cycles with 50-100% of SOC at 45°C and Cell 3 had 495 cycles with 0-50% of SOC at 45°C and had additional 1317 cycles with 50-100% of SOC at 45°C. Once cycled, these cells were opened in an argon glovebox and the anode material was prepared without cleaning to avoid removal of the SEI or dissolution of ionic species. Samples were mounted using carbon tape and transferred to the analysis chamber with < 1 minute of exposure to air. XPS depth profiling was performed using a Thermo K-Alpha (Al Kα peak) with an 1000keV Ar+ ion beam. TOF-SIMS depth profiling was performed using an Ion- ToF-SIMS5-300 configured with a 25keV Bi+ primary liquid metal ion gun. The sputter rates for TOF-SIMS and XPS were calibrated vs. a 100 nm layer of SiO2 grown on a Si wafer. SEI thickness was measured by FIB/SEM as well as the C+ profile and graphitic carbon in TOF-SIMS and XPS respectively and was found to be ~150 nm thick and grow by 50nm after cycling. The ionic concentration of Mn+ was observed to be inhomogeneously distributed within the SEI which may be used to estimate the Mn+ dissolution and migration behavior in anode materials. Acknowledgement: This work was partially supported by the American Honda Motor Co., Inc. References  E. Peled, D. Golodnitsky et al, “Composition, depth profiles and lateral distribution of materials in the SEI built on HOPG-TOF SIMS and XPS studies,” Journal of Power Sources, vol. 97-98, pp. 52-57, Jul. 2001.  H. Ota, Y. Sakata, A. Inoue, and S. Yamaguchi, “Analysis of Vinylene Carbonate Derived SEI Layers on Graphite Anode,” J. Electrochem. Soc., vol. 151, no. 10, p. A1659-A1669, Oct. 2004.  J. Benson, N. Nitta, J. T. Lee, A. Magasinski, I. Kovalenko, T. Fuller, and G. Yushin, “Comparative Study of the SEI on Graphite in Full Li-ion Battery Cells Using XPS, SIMS, and Electron Microscopy,” submitted 2012.
3:00 AM - C3.02
Catalytic Properties of Chemically Exfoliated 2D Layered Transition Metal Dichalcogenides
Damien Adrien Voiry 1 Hisato Yamaguchi 1 Junwen Li 2 Rafael Silva 3 Diego C. B. Alves 1 Takeshi Fujita 4 7 Mingwei Chen 4 Tewodros Asefa 3 Vivek Shenoy 2 Goki Eda 5 6 Manish Chhowalla 1
1Rutgers University Piscataway USA2Brown University Providence USA3Rutgers University Piscataway USA4Tohoku University Sendai Japan5National University of Singapore Singapore Singapore6National University of Singapore Singapore Singapore7JST, PRESTO Saitama JapanShow Abstract
Layered Transition Metal Dichalcogenides (LTMDs) can be exfoliated to atomically thin 2D nanosheets. The monolayered 2D nanoshseets have dramatically interesting properties. MoS2 can be exfoliated chemically via lithium intercalation and the properties are significantly different from the bulk material as well as mechanically exfoliated MoS2 . We have investigated the influence of the chemical exfoliation parameters on the electro-catalytic performance for various LTMDs. Specifically, we have measured the hydrogen evolution reaction (HER) properties of LTMDs. We have found that chemical exfoliation leads to a dramatic enhancement of the HER catalytic properties and we have observed that this improvement is correlated to modifications of the atomic and electrronic structure of LTMDs due to the chemical exfoliation. Density functional theory calculations confirm that the highly strained structure induced by the atomic displacement during the lithium intercalation has a great influence on the ability of these LTMDs to evolve hydrogen at low overpotential.  Eda, G. et al. Nano Lett. 11, 5111-5116 (2011).
3:15 AM - C3.04
Coupling In-Situ Techniques to Analyze Zinc Deposition and Dissolution for Energy Storage Applications
Jayme Keist 1 2 Christine Orme 2 Bassem El-Dasher 2 Sharon Torres 2 Jan Ilavsky 3 Frances Ross 4 Dan Steingart 5 Paul Wright 1 James Evans 1
1University of California - Berkeley Berkeley USA2Lawrence Livermore Natl Lab Livermore USA3Argonne Natl Lab Argonne USA4IBM T. J. Watson Research Center Yorktown Heights USA5City College New York New York USAShow Abstract
Zinc is an attractive material for energy storage since it is both inexpensive and energy dense (both gravimetrically and volumetrically). Zinc based energy storage has already been proven to exhibit high cyclability in rechargeable zinc-flow batteries and has exhibited high energy densities in primary zinc-air batteries. The zinc electrode, however, is typically the limiting electrode in rechargeable applications since detrimental morphologies such as dendrites can form during deposition leading to reduced cyclability. This research focuses on understanding the dynamics of the zinc deposition and dissolution processes in both aqueous alkaline electrolytes and ionic liquid based electrolytes. The goal of this research is to link the early nucleation and growth behavior to the formation of detrimental morphologies. This research couples three in-situ analysis techniques: electrochemical optical microscopy (EC OM), electrochemical atomic force microscopy (EC AFM) and electrochemical ultra-small-angle x-ray scattering (EC USAXS). These in-situ analysis techniques are complimentary in terms of length and time scales accessible and allow for the analysis of zinc deposition and dissolution from the sub-nanometer to micron regime. From the AFM analysis, feature shapes, aspect ratios, and size distributions were quantified and these results were used to build the model that analyzed the USAXS scattering data. Subsequent ex-situ SEM characterization was conducted to verify the morphologies observed by the in-situ techniques during deposition. This talk also compares and contrasts the deposition behavior of zinc within an aqueous alkaline electrolyte and within an ionic liquid electrolyte. Portions of this work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
3:30 AM - C3.05
Viologen Modified Conducting Polymers: A Polymer-based Battery Anode
Sujat Sen 1 James Saraidaridis 2 SungYeol Kim 2 G. Tayhas R. Palmore 1 2
1Brown University Providence USA2Brown University Providence USAShow Abstract
We previously demonstrated a battery fabricated from polypyrrole (pPy) doped with redox active dopants. This battery was shown to deliver higher energy density than that of commercial electric double-layer capacitors at high power demands. This battery consisted of pPy doped with ABTS (pPy[ABTS]) and pPy doped with indigo carmine (pPy[IC]) forming the cathode and anode respectively, with a cell emf of 0.5 V. Other candidates for cathode and anode dopants are being considered to increase the cell emf. Viologens or 4, 4&’-bipyridine derivatives are versatile compounds with three different oxidation states (i.e., V0, V+. and V2+). They are known for their negative redox potentials and rapid rates of electron transfer, and thus are good candidates for increasing the cell emf of the original battery when used in the anode. Typical examples include benzyl and methyl viologens, which have reversible redox chemistries centered at -0.5 and -0.9 V (vs.SCE). Different approaches have been used to incorporate viologens into a polymer matrix,[3, 4] although previous reports did not utilize the redox capacity of viologens for energy storage. We report on the stability and performance of films of conducting polymers (CP) containing viologen molecules, bound either by electrostatic or covalent means. To incorporate electrostatically a viologen molecule as an anionic dopant to a polycationic pPy, it structure must be modified to possess sulfonate groups (i.e. a disulfonated viologen or a tetra-sulfonated viologen). This structural modification ensures that viologen is anionic during electropolymerization of the CP and hence incorporated into the polycationic matrix. Alternatively, viologens can be attached directly to the pyrrole monomer via covalent linkage to an N-substituted pyrrole. This viologen substituted pyrrole monomer was then electropolymerized to obtain a polymer film to be used as the anode. All polymer films exhibited the distinct redox activity of the viologen dopant, however the covalent composite exhibited the best charge-discharge behavior as determined by galvanostatic testing with a maximum capacity of 55mAh/g. References 1. H.K. Song et al, Adv.Mater., 18 (2006) 1764-1768. 2. C.L. Bird et al, Chem.Soc.Rev.10 (1981) 49-82. 3. M.S. Wrighton et al, J.Phys.Chem., 92 (1988) 5221-5229. 4. G. Bidan et al, J.Chem.Soc.Chem.Commun., (1984) 1185-1186. 5. Y. Kawanishi et al, J.Phys.Chem., 90 (1986) 2469-2475
3:45 AM - C3.06
Improvement in Output Performance and Cycling Behaviors of a Metal Hydride/Air Secondary Battery
Masatsugu Morimitsu 1 Yuuki Tsuchinaga 1 Naoki Osada 1 Motoki Mizutani 1 Akari Miwa 1 Yoshihiro Wada 2
1Doshisha University Kyotanabe Japan2Kyushu Electric Power Inc. Fukuoka JapanShow Abstract
A metal/air battery is one of the promising candidates for a next generation of secondary battery which is possible to show higher energy density than current lithium ion batteries. Especially, the air battery using a metal hydride negative electrode and an alkaline aqueous solution, i.e., metal hydride/air battery, is expected to show such a high energy density and maintain safety even though the capacity increases, because the negative electrode uses no less noble metal such as lithium, sodium, or magnesium. This paper presents our recent results of metal hydride/air secondary batteries using an alkaline aqueous solution with a metal hydride negative electrode and a nickel-based air electrode. The negative electrode consisted of MH powders supported by a nickel form, and the air electrode was a mixture of nickel powders, bismuth-iridium composite oxide as catalyst, and PTFE binder. The cell comprising a single negative electrode, a single positive electrode, and a separator with an alkaline solution was examined at constant current at ambient atmosphere, and the polarization behaviors and cycling performance were discussed. The results indicated some excellent properties for charge-discharge cycles such as high energy density more than 400 Wh/L and stable voltages for 300 cycles or more. The capacity of the examined cells depended only on the negative electrode capacity, suggesting that the metal hydride/air battery has no limitation on the positive electrode capacity, because no plugging by discharge product occurs. This was quite different from the other air batteries using less noble metals and a particular feature of metal hydride/air batteries. This paper will also present the results of the cells comprising double positive electrodes and a single negative electrode between them.
C4: Batteries and Supercapacitors
Monday PM, November 26, 2012
Hynes, Level 3, Room 304
4:30 AM - C4.01
Investigation of Functionalized Electrode Performance in Vanadium Redox Flow Batteries
E. Agar 1 C. R Dennison 1 A. R. Kalidindi 1 K. W. Knehr 1 E. C. Kumbur 1
1Drexel University Philadelphia PA USAShow Abstract
Vanadium redox flow batteries (VRFBs) have emerged as a novel energy storage technology with great promise for grid-scale energy applications due to their high energy efficiency (70-85%) and long cycle life (12,000+ cycles). The power density of these systems is limited by the performance of the electrodes used in each half cell. Among currently studied electrode materials, carbon felt is of particular interest because of its high surface area and relatively low cost. The carbon felts are functionalized with thermal and acid treatments to increase their performance in VRFBs. To date, the performance of functionalized carbon felt electrodes has been studied only in symmetric configurations, where identical electrodes are used in positive and negative half cells. In this study, the performance of a VRFB in asymmetric electrode configurations is measured with raw and functionalized electrodes. A base case of functionalized electrodes in both half-cells was chosen for comparison since this combination is observed to provide the best performance. When the positive electrode in the base case is replaced with a raw felt, the efficiency is found to be comparable to that of the base case. However, when the negative electrode in the base case is replaced with a raw felt, a significantly lower efficiency is observed, suggesting that the negative electrode is limiting the performance. To determine the reason for this drawback, cyclic voltammetry is used to measure the reaction kinetics at raw and functionalized electrodes. At a specific electrode, the reaction rate constants are found to be roughly the same for the negative and positive half-cell redox reactions. However, the potential required for the reduction reaction at the negative electrode is observed to cause hydrogen evolution, which reduces the performance of the cell. The reaction kinetics data suggests that the lower negative electrode performance is not due to a slower reaction rate, but rather because of the presence of hydrogen evolution.
4:45 AM - C4.02
Reducing Capacity Loss in Vanadium Redox Flow Batteries by Controlling Convective Transport Across the Membrane
K. W. Knehr 1 E. Agar 1 C. R. Dennison 1 A. R. Kalidindi 1 E. C. Kumbur 1
1Drexel University Philadelphia PA USAShow Abstract
Vanadium redox flow batteries (VRFBs) are an emerging technology for grid-scale energy storage applications because the energy and power densities are decoupled, which enables scalable energy storage with the potential for high energy efficiency (70-85%) and long cycle life (12000+ cycles). However, currently the long-term performance of these batteries is severely limited due to the crossover of vanadium ions through the membrane. Species crossover leads to the depletion of vanadium ions in one half-cell, which reduces the system&’s overall capacity (available charge) with each cycle, and presents a major obstacle to widespread implementation of VRFBs. Most of the efforts to reduce crossover, both experimental and computational, are focused on tailoring the structure and properties of the membrane to reduce the vanadium crossover across the membrane. In this work, a transient, two-dimensional, VRFB performance model is developed that accounts for convection, diffusion, and migration across the membrane. By incorporating all these three transport modes, this model allows for more accurate predictions of the capacity loss experienced during long-term performance. Using the model, different case studies are conducted and the relative contributions of each transport mechanism are determined. The results of long-term performance studies show that convective transport in particular contributes significantly to the capacity loss during VRFB operation. To reduce the impact of convective transport on the species crossover, different electrolyte management strategies are explored.
5:00 AM - C4.03
Novel Flow Battery Chemistries
Brian Huskinson 1 Michael J Aziz 1
1Harvard School of Engineering and Applied Sciences Cambridge USAShow Abstract
Flow batteries are a potentially important technology for grid-scale electrical energy storage in the face of rising electricity production from intermittent renewables like wind and solar. Many chemistries and configurations could be used in the operation of a flow battery, and this presentation will focus on some that we find particularly promising. We have developed novel alloy oxide electrocatalysts that have permitted the development of a hydrogen-chlorine flow battery with power densities exceeding 1 W/cm2 with a precious metal loading of about 0.1 mg/cm2. The cell exhibits virtually no activation loss, allowing for very high efficiency operation. The effects of varying operating parameters and cell design will be discussed, along with substantive comparisons to a quantitative model of this device. Alternate chemistries, including the use of small organic molecules in a flow battery setup, will be discussed, highlighting some promising preliminary results from our lab. The advantages of using such compounds will be shown.
5:15 AM - C4.04
Supercapacitors Based on MnO2 and Graphene- MnO2 Nanocomposite Materials
Mohamad Khawaja 1 Manoj Ram 1 Yogi Goswami 1 Elias Stefanakos 1
1University of South Florida Tampa USAShow Abstract
Electrochemical supercapacitors have high energy density with an excellent reversibility, and operate at greater specific power than most rechargeable batteries. Therefore, research has been focused on improving the novel materials, and methods to enhance the operation of supercapacitors. Activated carbon metal oxides (manganese oxide ‘MnO2&’ and ruthenium oxide ‘RuO2&’) take advantage over conducting polymers for their stability. Mixing conducting polymers and metal oxides has recently been investigated to understand the behavior and stability of the hybrid supercapacitor. This research project focuses on supercapacitor electrodes coated with MnO2 and graphene (G)-MnO2 synthesized materials. The G-MnO2 and MnO2 nanomaterials were synthesized using sol-gel technique. The MnO2 and G-MnO2 materials were characterized using electrochemistry, Scanning Electron Microscopy (SEM), Raman spectroscopy, X-ray-diffraction, and Transmission Electron Microscopy (TEM) techniques. The synthesized G-MnO2 and MnO2 powder were mixed with nafion and coated on graphite electrodes. The cyclic voltammogram, charging-discharging, stability and life cycle of the various MnO2 and MnO2 materials were studied in supercapacitor configurations. This study provides a fundamental understanding for high performance synthesized MnO2 as well as G-MnO2 material. The high specific capacitance and stable charging -discharging cycles have been observed in G-MnO2 containing equal ratio of graphene to MnO2. This study provides a fundamental understanding of supercapacitor applications for high performance synthesized MnO2 and G-MnO2 nanoparticles. Based on our experimental data shown in this work, we believe that G-MnO2 material could be exploited for commercial purposes.
5:30 AM - C4.05
Nanoscale Characterization of CDC Supercapacitors by In situ Scanning Probe Microscopy Methods
Thomas Arruda 1 Stephen Jesse 1 Min Heon 2 Volker Presser 2 Yury Gogotsi 2 Nina Balke 1
1Oak Ridge National Laboratory Oak Ridge USA2Drexel University Philadelphia USAShow Abstract
Supercapacitors offer high energy density electrochemical charge storage without the necessity of Faradaic charge transfer processes. In contrast to batteries, they can be cycled hundreds of thousands of times with minimal performance losses.1 One of the major factors limiting the longevity of batteries is caused by the significant strains induced during intercalation processes.2 Supercapacitors store charge in the electrochemical double-layer and therefore should undergo little to no mechanical fatigue. However, numerous electrochemical dilatometric studies3-5 have indicated that the carbonaceous electrodes employed in supercapacitors can exhibit strain on the order 1 to 10 %. Such strain processes can lead to diminished lifetime. These strains are believed to be attributed to meso and micropore swelling during charge/discharge cycles. Other studies have identified intercalation processes as possible explanations for the larger than expected volume expansion. Electrochemical dilatometry is a useful tool to observe large changes in material volume during cycling. However, these measurements are performed on relatively large working electrode areas, precluding any microscopic volume changes (i.e. changes to volume on individual grains or pores). Such information would be valuable in diagnosing potential failure or cell lifetime issues. Scanning probe microscopy (SPM) is capable of measuring surface deformations as small as 10s of picometers, thus offering a promising avenue to study minute volume changes in supercapacitor materials. Additionally, the lateral resolution of modern AFM instruments is sufficient to resolve individual grains and defects. Therefore we are capable of measuring very small volume expansion on single particles or defects. Here, we investigate Carbide Derived Carbon (CDC)6 supercapacitor electrodes by in situ SPM methods. The CDC films are placed in an in situ AFM electrochemical cell and cycled during AFM topographical measurements. The volume change that occurs as a result of cycling is evident in the topographical image, allowing us to investigate the kinetics of double layer formation. This allows us to study the role of ion intercalation as it pertains to the observed volume changes and separate it from that of double-layer formation. Additionally, ion size effects on pore/particle swelling can also be investigated by these methods. This talk will highlight our recent findings. Research at ORNL was supported by the Fluid Interface Reactions, Structures and Transport (FIRST) Center, ORNL, an Energy Frontier Research Center funded by DOE, Office of Science, Office of Basic Energy Sciences (ERKCC61). Work was conducted at the Center for Nanophase Material Sciences, which is sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy.
C1: Oxygen Reduction I
Monday AM, November 26, 2012
Hynes, Level 3, Room 304
9:45 AM - *C1.01
Bridging the Gap for Electrocatalysis of O2 in Water-based and Organic-based Electrolytes
Nenad Markovic 1 Ram Subbaraman 1 Dusan Strmcnik 1 Dusan Tripkovic 1 Chao Wang 1 Gustav Wiberg 1 Jakub Staszak Jirkovsky 1 Nemanja Danilovic 1 Dennis Van der Vliet 1 Pietro Papa Lopes 1 Arvydas Paulikas 1 Vojislav Stamenkovic 1
1Argonne National Lab Lemont USAShow Abstract
Design and synthesis of energy efficient and stable electrochemical interfaces (materials and double layer components) with tailor properties for accelerating and directing chemical transformations is the key to developing new alternative energy systems - fuel cells, electrolyzers and batteries. In aqueous electrolytes, depending on the nature of the reacting species, the supporting electrolyte, and the metal electrodes, two types of interactions have traditionally been considered: (i) direct - covalent bond formation between adsorbates and electrodes, involving chemisorption, electron transfer, and release of the ion hydration shell; and (ii) relatively weak non-covalent metal-ion forces that may affect the concentration of ions in the vicinity of the electrode but do not involve direct metal-adsorbate bonding. The range of physical phenomena associated with these two classes of bonds is unusually broad, and are of paramount importance to understand activity metal-electrolyte two phase interfaces. In the past, researcher working in the field of fuel cells (converting hydrogen and oxygen into water) and electrolyzers (splitting water back to H2 and O2) ) seldom focused on understanding the electrochemical compliments of these reactions in battery systems, e.g., the lithium-air system. In this lecture, we address the importance of both covalent and non-covalent interactions in controlling catalytic activity of electrochemical interfaces. Although the field is still in its infancy, a great deal has already been learned and trends are beginning to emerge that give new insight into the relationship between the nature of bonding interactions and catalytic activity/stability of electrochemical interfaces. In addition, to bridge the gap between the “water battery” (fuel cell harr; electrolyzer) and the Li-air battery systems we demonstrate that this would require fundamentally new knowledge in several critical areas. We conclude that understanding the complexity (simplicity) of electrochemical interfaces would open new avenues for design and deployment of alternative energy systems.
10:15 AM - C1.02
Enhanced Oxygen Reduction Activity of Platinum Monolayer with a Gold Interlayer on Palladium
Minhua Shao 1 Amra Peles 2 Jonathan H Odell 1
1UTC Power South Windsor USA2United Technologies Research Center East Hartford USAShow Abstract
Core-shell catalysts have attracted significant attention for various chemical reactions due to their higher utilization of costly noble metals, activity improvement caused by electronic and structural effects from the core materials.Recent studies have demonstrated that the ORR activity of Pt monolayer can be further tuned by an interlayer. For instance, with a Pd9Au alloy sublayer between Pt monolayer and Pd nanoparticle, the ORR activity can be enhanced by 70%. The role of the sublayers in the activity enhancement is unclear. We report here the ORR activity improvement on Pt monolayer supported on conventional Pd nanoparticles by introducing an Au submonolayer (~60% coverage) between the Pd core and Pt shell. The activity of Pt/Au/Pd/C is ~2 and 7 times higher than that of Pt/Pd/C and Pt/C, respectively. By controlling the shape (cubic and octahedral) of the Pd cores, we are able to distinguish the role of Au on the activity improvement at different facets. Our results demonstrate that the Au interlayer can enhance the Pt monolayer activity toward oxygen reduction on both (100) and (111) surfaces, with the enhancement on (100) much more pronounced. The density functional theory (DFT) calculations were conducted to explain this observation and will be discussed in the meeting.
10:30 AM - C1.03
Structurally Ordered Intermetallic Nanoparticles as Electrocatalysts for the ORR
Deli Wang 1 2 Yingchao Yu 1 Huolin Xin 1 David A Muller 1 Hecter D Abruna 1
1Southwest University Chongqing China2Cornell University Ithaca USAShow Abstract
One of the main barriers to the commercialization of fuel cells is the catalysts which generally consist of Pt-based precious metals. Since Pt is costly and scarce, it poses the question of how to lower the Pt loading and increase its efficiency. Most previous studies focused on Pt alloyed with some 3d-transition metals, such as Fe, Co, Ni, etc. However, the activity and stability are not good enough for fuel cell applications. Recently, ordered intermetallic nanoparticles have attracted some attention, since the ordered intermetallic phase provides definite composition and structure. They can provide predictable control over structural, geometric, and electronic effects, which are not afforded by alloys. However, previous reports on ordered intermetallics were focused on anode catalysts. In addition, the synthesis procedures tend to be complex. Moreover, the particles are unsupported and it is not easy to clean the particle surface. We present data on carbon supported ordered intermetallic nanoparticles that can be easily formed using a simple impregnation-reduction method followed by high temperature treatment. We will discuss two main subjects in this talk: (1) Structurally ordered intermetallic Pt3Co@Pt/C Core-Shell nanoparticles as oxygen reduction reaction (ORR) catalysts, and (2) Dealloying study of Cu3Pt/C ordered intermetallic nanoparticles for ORR catalysis. For Pt-Co nanoparticles, ordered Pt3Co intermetallic cores with a 2-3 atomic-layer thick platinum-rich shell were found according to electron energy loss spectroscopic (EELS) mapping. These nanoparticles showed over 200% increase in mass activity and over 300% increase in specific activity when compared to disordered Pt3Co alloy nanoparticles for the ORR. Stability tests showed a minimal loss of activity after 5,000 potential cycles and according to EELS mapping the ordered core-shell structure was maintained virtually intact. Two dealloying methods (electrochemical and chemical) were implemented to control the atomic-level morphology and enhancing the performance for the ORR. It was found that the electrochemical dealloying method resulted in formation of a thin Pt skin of ca. 1 nm with an ordered Cu3Pt core structure, while the chemical leaching gave rise to a spongy structure, with no ordered structure being preserved. Both dealloying methods yielded enhanced specific and mass activity toward the ORR and higher stability relative to Pt/C. The chemically dealloyed nanoparticles exhibited better mass activity than electrochemically dealloyed particles after 50 potential cycles, although with a slight lower specific activity. In both cases, there wea an enhancing in activity even after 5000 potential cycles. These findings are important to build next-generation fuel cell catalytsts.
10:45 AM - C1.04
Atomic-scale Compositional Mapping and 3-Dimensional Electron Microscopy of Oxygen Reduction Electrocatalysts for PEM Fuel Cells
Zhongyi Liu 1 Yingchao Yu 2 Nalini Subramanian 3 Zhiqiang Yu 3 Huolin Xin 4 Ye Zhu 5 Julia A Mundy 5 Randi Cabezas 5 Robert Hovden 5 Junliang Zhang 3 Rohit Makharia 3 David A Muller 5 Frederick T Wagner 3
1General Motors Warren USA2Cornell University Ithaca USA3General Motors Honeoye Falls USA4Cornell University Ithaca USA5Cornell University Ithaca USAShow Abstract
Pt-M (M is an element less noble than Pt) alloy catalysts are a useful pathway to reduce the amount of Pt needed to adequately catalyze the slow oxygen reduction reaction (ORR) at the cathode of proton exchange membrane (PEM) fuel cells. The Pt-M alloy catalysts have the potential to lower the Pt cost per vehicle from the current level of several thousands of dollars (calculated from a Pt-metal catalyst with a mass activity of 0.1 A/mgPt at 900 mV vs. reversible hydrogen electrode) to levels acceptable for mass production of PEM fuel cell vehicles. Interactions between Pt and M in the form of geometric and/or ligand effects are believed to be responsible for the enhanced activity of Pt-M alloy vs pure Pt catalysts. To finely tune the geometric and ligand effects for the maximum activity, Pt-M alloy catalysts have been engineered into small particles (a few nanometers) with complex chemistry and microstructure. In this presentation, we will first review examples of various types of Pt-M alloy catalysts that have been studied in our labs. We determined the Pt shell thickness and the distribution of Pt and M within the Pt-M alloy nanoparticles by using atomic-scale compositional mapping based on electron energy loss spectroscopy (EELS) in an aberration-corrected scanning transmission electron microscopy (STEM). We also determined the interior structure of the Pt-M alloy nanoparticles and their dispersion on the catalyst support by using 3-dimensional tomography in the STEM mode. We will then discuss and comment on the links between the fundamental findings and their practical relevance to the performance enhancements and Pt-loading reduction in fuel cell vehicles.
C2: Alkaline and Direct Oxidation Fuel Cells
Monday AM, November 26, 2012
Hynes, Level 3, Room 304
11:30 AM - *C2.01
Ni-based Electrocatalysts for Direct Oxidation Alkaline Fuel Cells Based on Ammonia and Ethanol
Evans Monyoncho 1 2 Anis Allagui 1 Saad Sarfraz 1 Tom Woo 2 Elena A. Baranova 1
1University of Ottawa Ottawa Canada2University of Ottawa Ottawa CanadaShow Abstract
Recent progress on alkaline anion-exchange membranes that conduct the negatively charged OH- has opened up the way to further develop direct alkaline fuel cells. Electrocatalysis of redox reactions is facilitated in alkaline electrolytes because, unlike in acidic media, there is a minimum poisoning thanks to weak bonding of the chemisorbed intermediates on the catalyst surface . Alkaline fuel cells are economically more advantageous because of the abundant and cheap non-precious metal catalysts. Ethanol is an attractive fuel for direct ethanol fuel cells due to its high energy density (8.30 kWh kg-1) and its ease in handling and production from the biomass. The state of the art electrocatalysts for ethanol oxidation in both alkaline and acidic media still lack the capability to cleave the C-C bond at low temperature, and produce CO2 as a final product . Ammonia is considered a major toxic pollutant of domestic, industrial and agricultural waters and its removal is very essential for ecological reasons. Additionally, anhydrous liquid NH3 is a compact H2 carrier as well as a distribution and storage medium. It can be directly used as a fuel in direct ammonia fuel cells as the theoretical specific charge of complete ammonia oxidation to N2 is 4.75Ah/g that is 95 % of the charge of methanol oxidation to CO2. The requirements of recent electrochemical studies to oxidize ammonia consist on finding high-performance electrocatalysts with low overpotential and low production of NOx and COx. While platinum group metals (PGM) and its bi-metallic alloys (e.g. PtIr, PtRu, PtPd, PtSnO2) exhibit the highest degradation strength and stability towards this process [3,4], their application at industrial scale is limited due to economical constraints, and therefore, there is an urgent need to utilize non-PGM catalysts. The aim of our current projects is to investigate the electrooxidation of ethanol and ammonia on NixPd1-x nanoparticles in alkaline media. To achieve this goal our strategy is (i) to synthesize predominately Ni-based bimetallic nanoparticles of uniform size and well-defined composition and structure (ii) use SEM/TEM, XRD, and XPS for their morphological and surface characterization and (iii) use electrochemical methods to evaluate the catalytic performance of the products with real-time monitoring of the electrooxidation reactions by in situ PM-IRRAS. The wealth of information from these experimental techniques is coupled with surface-decomposition DFT calculations for deeper understanding of the reaction network and prediction of the best electrocatalysts.  Beden, B.; Leger, J. M.; Lamy, C. In Brockris, J. O., Conway, B. E. and White, R. E., Eds.; Modern Aspects of Electrochemistry; Plenum Press: New York, 1992; Vol. 22, pp 97.  Yu, E. H.; Krewer, U.; Scott, K. Energies 2010, 3, 1499-1528.  Vitse, F.; Cooper, M.; Botte, G. J. Power Sources 2004, 142, 18-26.  Endo, K.; Katayama, Y.; Miura, T. Electrochim. Acta 2005, 50, 2181.
12:00 PM - C2.02
Thickness Dependence of Oxygen Reduction Activity on Epitaxial LaMnO3 Thin Films
Kelsey A. Stoerzinger 1 Marcel Risch 2 Zhenxing Feng 2 Jin Suntivich 1 Lv Weiming 3 Michael D. Biegalski 4 Hans M. Christen 4 . Ariando 5 T. Venkatesan 3 5 Yang Shao-Horn 1 2
1Massachusetts Institute of Technology Cambridge USA2Massachusetts Institute of Technology Cambridge USA3National University of Singapore Singapore 117576 Singapore4Oak Ridge National Laboratory Oak Ridge USA5National University of Singapore Singapore 117542 SingaporeShow Abstract
The characterization of oxide catalysts is often limited by heterogeneity of exposed surfaces and the composite nature of electrodes within fuel cells . Epitaxial thin films can provide well-defined surfaces of known orientation, the nature of which can be tuned through interaction with the substrate, via strain and variation of the electronic structure . We have fabricated (001) epitaxial films of LaMnO3 on Nb-doped SrTiO3 and investigated the relationship between film thickness and catalytic activity for the oxygen reduction reaction (ORR) in an alkaline environment. The activity decreases with film thickness; electrochemical measurements using the facile redox couple  [Fe(CN)6]3-/4- suggest that this trend is related to the ability to inject charge, arising from changes in the electronic structure of the film. Below a critical thickness around 10 nm, we observe distinct changes in film capacitance and interaction of the LaMnO3 with water. References:  J. Suntivich, H. A. Gasteiger, N. Yabuuchi, and Y. Shao-Horn, J. Electrochem. Soc. 157, B1263 (2010).  J. Fujioka, M. Nakamura, M. Kawasaki, and Y. Tokura, J. Appl. Phys. 111, 016107 (2012).  P. Chen, M. A. Fryling, and R. L. McCreery, Anal. Chem. 67, 3115 (1995).
12:15 PM - C2.03
Characterization of Alkaline Anion Exchange Membrane Material for Fuel Cell Applications
Jimmy John 1 Henry Kostalik 1 Kristina Hugar 1 Eric Rus 1 Geoffrey Coates 1 Hector Abruna 1
1Cornell University Ithaca USAShow Abstract
Compared to the well-known proton exchange membrane fuel cells (PEMFC), alkaline fuel cells (AFCs) offer high degree of versatility both in terms of fuels and electro-catalysts. In addition to hydrogen, economically viable small organic molecules such as methanol and ethanol can be potentially used as fuels as their oxidation has been indicated to be enhanced in alkaline media. Also, instead of traditional platinum-based catalysts, less expensive metals such as silver could be used. However, AFCs have been plagued by carbonation wherein there is buildup of solid carbonate in the porous matrix saturated with base. This leads to loss of ionic conductivity and eventual device failure. Use of alkaline anion exchange membrane (AAEM) as the ion conducting medium can potentially counter carbonation due to the absence of mobile cations in the membrane. AAEMs are, thus, critical to the realization of high performing alkaline fuel cells. However, fundamental studies on this new class of functional polymer materials are yet to be carried out. In our study, we have extensively characterized a prototypical quaternary ammonium based AAEM material. In a systematic approach, categorical studies focusing on various fundamental aspects of a practical AAEM have been carried out: (i) Physical transport - Movement of molecules through the membrane was investigated by rotating disc electrode (RDE) voltammetry using neutral probe molecules. (ii) Charge transport - Charge conduction pathways through the network of cationic ion-exchange sites were probed electrochemically using negatively charged redox probe molecules. (iii) In-situ determination of carbonate formation - Electrochemical quartz crystal microbalance studies were conducted to test for carbonate uptake in the membrane. A complimentary study focusing on the swelling of the membrane in water and in presence of fuels such as methanol using acoustic impedance spectroscopy was also undertaken. (iv) Fuel cell testing - Preliminary device testing was also carried out with membrane electrode assemblies constructed using the AAEM material. This study represents an essential step in our understanding of a class of functional polymer materials that is poised to become one of the critical components driving future energy technologies, specifically alkaline fuel cells.
12:30 PM - C2.04
Development of Ni-alloy Nanoparticle Catalysts for Anion Exchange Membrane Water Electrolysis
Michael K Bates 1 Sanjeev Mukerjee 1
1Northeastern University Boston USAShow Abstract
Anion exchange membranes (AEMs) open an exciting door for the development of non-Pt group metal (PGM) catalysts in fuel and electrolysis cells. Operation in alkaline media enables overcoming the “stability criterion” problem of the acid analog, which restricts its use to PGM catalysts. AEMs allow the use of inexpensive transition metal (TM) catalysts for both hydrogen evolution/oxidation reactions (HER/HOR) and oxygen evolution/reduction reactions (OER/ORR). Activity of TM electrodes relative to PGM is a function of several factors including inner/outer sphere charge transfer, changes in coverage of spectator ions and changes to the nature of the transition state. At a certain performance barrier, the cost per kWh or kgH2 will undoubtedly out-compete PGM electrocatalysts. The low cost and abundance of TM catalysts should pave the way for the commercialization of clean portable power devices. Water electrolyzers can produce H2(g) for ~$5/kg, slightly more than the comparable metric of $/gal gasoline, largely due to expensive PGM catalysts required. The development of Ni-alloy electrocatalysts will significantly decrease this cost. Although the OER is the primary source of overpotential in PEM electrolyzers, this may not be the case for AEMWEs. Pletcher et al. (PCCP 2010) have observed excellent OER activity from electrodeposited Ni-Fe catalysts. RDE results in our lab have shown that high surface area Ni-Fe-Mo catalysts can outperform even standard IrO2 nanoparticle catalysts, with in-house samples achieving ~200A/g @eta;=370mV compared to ~30A/g for IrO2 at the same over-potential. Studies are currently underway to test and optimize the OER activity of novel Raney Ni-alloys and Ni-alloy nanoparticles at the AEM interface. On the hydrogen side, Ni and previously studied Ni-alloys require a large Δeta; vs. standard Pt catalysts to achieve similar current density. However, recent RDE results have significantly decreased the gap between Ni-alloy and Pt HER performance. Ni-Mo electrodes have long exhibited the best non-PGM HER activity. The electrocatalytic properties of Ni-Mo alloys have been explained by Brewer-Engel theory in terms of optimized Hads bond strength versus other TM alloys. However, recent RDE results show greatly increased performance from Ni-Cr alloys and layered Ni/TM-oxide/C catalysts. Although the cause of increased performance is still under investigation, the answer may lie in synergistic “spillover” effects resulting from the highly reversible redox properties of some TM-oxides in alkaline media. Lyons et al. (JEAC 2010) have recently investigated the OER on TMs and their passivating surface oxides and developed a model of hydrous oxy-hydroxide films which increase the electrochemical surface area and OER activity of TM electrodes. It seems plausible that these oxy-hydroxide films could facilitate the “spillover” or surface effusion of OHads & Hads at relevant OER & HER potentials, increasing reaction kinetics and cell performance.
12:45 PM - C2.05
Electrolysis of Alcohols in HighTemperature/High Pressure Water
Asli Yuksel 1 Mitsuru Sasaki 2 Motonobu Goto 3
1Izmir Institute of Technology Izmir Turkey2Kumamoto University Kumamoto Japan3Nagoya University Nagoya JapanShow Abstract
The design of clean, efficient and environmentally friendly routes has become a central issue of chemical research both in industry and academia. One of the approaches being used in green chemistry practices is to use water as a solvent and reaction medium where possible. Much of this work deals with liquid water at temperatures exceeding the normal boiling point which is denoted as sub-critical water. Electrochemical reaction, usually operated at atmospheric condition in water, is generally slow, although it has advantages over chemical reaction such as suppression of side reaction by tuning operating conditi