Faisal Alamgir, Georgia Institute of Technology
Dario Arena, Brookhaven National Laboratory
John Baniecki, Fujitsu Laboratories
William C. Chueh, Stanford Univeristy
Gyula Eres, Oak Ridge National Laboratory
YY3: Spectroscopy from First Principles and Photon-In/Photon-Out Methods I
Tuesday PM, April 07, 2015
Marriott Marquis, Yerba Buena Level, Nob Hill A/B
2:30 AM - *YY3.01
Electronic Reconstruction of in-situ Grown Ultra-Thin NdNiO3 Films in Proximity to a Magnetic Underlayer
Milan Radovic 1 Rajendra Dhaka 2 Zoran Ristic 3 Nicholas Plumb 1 Zhiming Wang 1 Marisa Medarde 4 Ming Shi 1 Joel Mesot 3 5 6
1Paul Scherrer Institut Villigen Switzerland2Indian Institute of Technology Delhi India3Institute of Condensed Matter Physics EPF Lausanne Switzerland4Paul Scherrer Institut Villigen Switzerland5ETH Zurich Switzerland6Paul Scherrer Institut Villigen SwitzerlandShow Abstract
A compound from the RNiO3 family of strongly correlated oxides, NdNiO3 (NNO) exhibits temperature driven metal to insulator (MI) and magnetic transition (paramagnetic to antiferromagnetic one). To understand the role of magnetism on electronic structure of NNO we performed temperature dependent high-resolution angle-resolved photoemission spectroscopy (ARPES) study on perturbed electronic/magnetic structure of the ultra-thin film of NNO.
ARPES is a very surface sensitive technique which potential we fully utilized in combination with PLD. This approach gives us satiated control of the measured system. By using pulsed laser deposition (PLD), a bilayer systems consisting of underlying magnetically ordered film of La1-xSrxMnO3 (and La1-xCaxMnO3) and ultrathin film of NNO (2-5 u.c.) was created. By changing the content of Sr(Ca) we control magnetic ordering in the manganite layer from ferromagnetic metallic (x=0.33 , FM/M) to antiferromagnetic charged ordered one (x=0.66, AF/I). We have performed high#8208;resolution ARPES to map the electronic structure NdNiO3 films in 3D k#8208;space as a function of the temperature.
Obtained study gives important information about the influence of magnetic orders on the electronic structure and correlation effects in nickelates, with the potential to have a big impact on the field.
3:00 AM - YY3.02
Possible Mg Intercalation Mechanism at the Mo6S8 Cathode Surface Proposed by First-Principles Methods
Liwen Wan 1 David Prendergast 1
1Lawrence Berkeley National Laboratory Berkeley United StatesShow Abstract
Current Li-ion batteries, which have been the primary focus for electrical energy storage development in the past 40 years, are approaching their theoretical limits. Divalent Mg-ion battery technology, with potential high energy density and volumetric capacity, may provide alternative solutions to meet the fast-growing global demand for energy storage. The prototype Mg-ion battery system was established almost 15 years ago [D. Aurbach et al. Nature 407, 724 (2000)], where a complex organohaloaluminate/tetrahydrofuran (Mg(AlCl2BuEt)2/THF) solution is developed as the electrolyte that is sandwiched by a Mg metal (anode) and a Mo6S8 (cathode) to form the electrochemical cell. Despite the remarkable success of this prototype system, we still lack a clear understanding of the fundamental Mg intercalation/deposition mechanism at the electrolyte/electrode interfaces that perhaps results in the observed sluggish Mg transport process.
Our previous work has shown that the Mg-ion is strongly coordinated in the bulk electrolyte by a combination of counterion, Cl-, and organic aprotic solvent, THF. The solvation energy can easily exceed 2 eV due to the strong electrostatic interactions between Mg2+ and its ligands. [Wan and Prendergast, JACS 136, 14456 (2014)] With this information, one can imagine the difficulties to strip all its ligands away at the interface and allow Mg2+ to intercalate/deposit into the bulk electrolyte. In this work, we focus on the Mg2+ intercalation process at the Mo6S8 cathode surface. The solvent-surface interactions are first studied using density functional theory. With the presence of positively charged MgCl+ unit on the surface, a change of THF binding energy to the surface is observed. Upon Mg intercalation, the counterion Cl- is striped away from the surface and the dissociation energy between Mg2+ and Cl- is approximated using the nudged elastic band method. Finally, a complete Mg intercalation mechanism is proposed and the unique role of Mo6S8 as the cathode material is emphasized.
This work is supported as part of the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences.
3:15 AM - YY3.03
The Dependence of Li Conduction in Solid Electrolytes on the Local Electronic Structure and Bonding
Nicole Adelstein 1 Brandon Wood 1
1Lawrence Livermore National Laboratory Livermore United StatesShow Abstract
All-solid-state batteries have the potential to dramatically improve the capacity and safety of high-density energy storage. Inorganic electrolytes with sufficiently high conductivity and mechanical and thermal stability are needed to develop these batteries. Understanding the effect of the electronic structure on Li conductivity will provide design rules to improve promising materials accelerate high-throughput screening of potential electrolytes. Using a recently synthesized highly conductive electrolyte candidate, Li3InBr6, and other superionic electrolytes, we characterize the effect of the local electronic structure on Li diffusivity using first-principles molecular dynamics simulations. The insights gained from our in-depth characterization of the Li transport mechanism in this promising material will aid the search for better inorganic solid-state batteries.
This work was performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344.
3:30 AM - *YY3.04
Resonant Inelastic X-Ray Scattering to Discover, Design and Optimize Energy Materials
Ignace Jarrige 1
1Brookhaven National Lab Upton United StatesShow Abstract
The knowledge of the electronic structure is fundamental to the understanding of material properties, and therefore to the discovery and optimization of energy materials. Resonant inelastic x-ray scattering (RIXS) combines the potential of x-ray emission and x-ray absorption spectroscopies, simultaneously probing the occupied and unoccupied electronic structure in an element and orbital-specific fashion. A photon-in photon-out technique, RIXS has been applied to a growing range of in-situ and constrained sample environments since its inception in the mid-90s. Concurrently, the technique has also benefited from drastic improvements in energy resolution, reaching a level where simultaneous measurements of low-energy electronic, magnetic and structural excitations are now possible. I will report on a few recent applications of RIXS related to the study of superconductivity in 3d and 4f electron systems, and catalysis in 5d electron materials. Through these studies, I will show that RIXS is a powerful tool well suited for exploratory tasks in energy science, such as discovery of new superconductors and design or optimization of catalysts. I will also touch on the future of RIXS, as further improvements in energy resolution are soon expected with the current development of new instruments such as the SIX beamline at NSLS-II.
YY4: Spectroscopy from First Principles and Photon-In/Photon-Out Methods II
Tuesday PM, April 07, 2015
Marriott Marquis, Yerba Buena Level, Nob Hill A/B
4:30 AM - *YY4.01
Insights of Energy Conversion and Energy-Storage Materials from the in situ/Operando Soft X-Ray Spectroscopy Characterization
Jinghua Guo 1 Per-Anders Glans 1 Yi-Sheng Liu 1
1Lawrence Berkeley National Laboratory Berkeley United StatesShow Abstract
Advanced energy technology arises from the understanding in basic science, thus rest in large on in-situ/operando characterization tools for observing the physical and chemical interfacial processes in energy materials and devices, which has been largely limited in a framework of thermodynamic and kinetic concepts or atomic and nanoscale. In many important energy systems such as energy conversion, energy storage and catalysis, advanced materials and functionality in devices are based on the complexity of material architecture, chemistry and interactions among constituents within. To understand and thus ultimately control the energy conversion and energy storage applications calls for in-situ/operando characterization tools. We have developed the in-situ/operando soft X-ray spectroscopy for the studies of catalytic and electrochemical reactions in recent years, and overcome the challenge that soft X-rays cannot easily peek into the high-pressure catalytic cells or liquid electrochemical cells. The unique design of in-situ/operando soft X-ray spectroscopy instrumentation design and fabrication principle and a number of examples will be presented, including the nanocatalysts and the recent experiment performed for studying the hole generation in a specifically designed photoelectrochemical cell under operando conditions.
5:00 AM - YY4.02
In-Situ X-Ray Absorption Spectroscopy of Ionic Liquid Gated Ultra-Thin La0.7Sr0.3MnO3 Films
Bongju Kim 1 2 Hongtao Yuan 1 2 Hoyoung Jang 3 Yasuyuki Hikita 1 Christopher Bell 1 4 JunSik Lee 3 Harold Y Hwang 1 2
1SLAC National Accelerator Laboratory Menlo Park United States2Stanford University Stanford United States3SLAC National Accelerator Laboratary Menlo Park United States4University of Bristol Bristol United KingdomShow Abstract
Tuning the carrier density in transition metal oxides provides the opportunity to controllably access the various electronic phases such as metallic, insulating, and superconducting, commonly found in these materials. Recently, ionic liquid gated electric double-layer transistor (EDLT) structure has attracted much attention as an effective technique to modulate the carrier density beyond the typically accessible range by solid-state gating techniques [1-4]. Under such high carrier densities, a strong electronic structure modification is expected to occur locally at the oxide/ionic liquid interface. However, the understanding of the oxide/ionic liquid interface and the oxide electronic structure under ionic liquid gating conditions has been limited.
Here, we present a comprehensive study of electrical transport and in-situ X-ray absorption spectroscopy (XAS) in ionic liquid/gel gated ultra-thin La0.7Sr0.3MnO3 (LSMO) films to better understand the charge modulation effect by ionic liquid/gel gating. LSMO is a well known ferromagnetic metal in bulk at room temperature which has recently been reported to exhibit metal-insulator transition as the thickness is reduced [5-7]. The ultra-thin LSMO films prepared by pulsed laser deposition on SrTiO3 (001) substrates were coated with ionic liquid and a gate electrode to form the EDLT structure. By applying a negative bias to the gate electrode, a metallic state was stabilized which could be switched to an insulating state reversibly by applying a positive bias. To explore the origin of this phenomena, we employed in-situ XAS technique on these devices to probe the manganese valence state during the application of gate voltage. The Mn-L2,3 edge spectra showed features characteristic of valence change under application of bias which will be discussed in relation to the transport data.
 K. Ueno, et al., Nat. Mater. 7, 855 (2008).
 H. T. Yuan, et al., Adv. Funct. Mater. 19, 1046 (2009).
 M. Nakano et al., Nature 487, 459 (2012).
 J. Jeong, et al., Science 339, 1042 (2013).
 B. Kim, et al., Appl. Phys. Lett. 99, 092513 (2011).
 B. Kim, et al., Sol. Stat. Commun. 105, 598 (2010).
 M. Huijben, et al., Phys. Rev. B 78, 094413 (2008).
5:15 AM - YY4.03
In-Situ and Operando XAS Technique for Metal/Aqueous Solution Interface Characterization
Chenghao Wu 1 3 Haitao Fang 3 Jinghua Guo 2 Miquel B. Salmeron 2
1UC Berkeley Berkeley United States2Lawrence Berkeley National Laboratory Berkeley United States3LBNL Berkeley United StatesShow Abstract
Most of the electrochemistry processes occur within the thin layer of electrolyte at the electrolyte / electrode interfaces, commonly denoted as the electrical double layer (EDL). In spite of some classic EDL theories, very limited experimental information is available about these solvent or solute species within such EDLs. We have developed in-situ liquid cells to study such electrolyte / electrode interfaces by means of soft x-ray absorption spectroscopy.  With this in-situ and operando XAS technique, we characterized the interface between gold / platinum electrode and water or sulfuric acid solution. It was found that the interfacial water layer has significantly different hydrogen-bonding network structure compared to the bulk water. Under different bias, the polar water molecules will respond to the external electrical field and reorient at the gold electrode surface, which significantly changes the amount of distorted or broken hydrogen bonds.  We were also able to identify some intermediate surface species during Pt-catalyzed OER reaction under working conditions.
. J. J. Velasco-Velez, C. H. Wu, et al., Science, ASAP.
5:30 AM - *YY4.04
Combined In Situ Synchrotron Based X-Rays and Mass Spectroscopy Study on Thermal Stability of Cathode Materials for Li-Ion Batteries during Heating
Seongmin Bak 2 Enyuan Hu 2 Yongning Zhou 2 Xiqian Yu 2 Xiao-Qing Dr Yang 2 Kyung-Wan Nam 1
1Dongguk University Seoul Korea (the Republic of)2Brookhaven National Lab Upton United StatesShow Abstract
The safety issue of LIB has been considered as a one of the most crucial drawbacks that must be improved for the application of power sources of plug-in hybrid electric vehicles (PHEVs) and electrical vehicles (EV). One of the main reason that might cause safety hazards of the LIB cell is associated with the thermal instability of cathode materials, especially at their charged states. Reportedly, charged cathodes are unstable at high temperatures and exothermically decomposed with liberating oxygen. The released reactive oxygen may lead to an increased inner cell pressure and violent reactions with electrolytes heated above its flash point. Therefore, in-depth understanding of the thermal decomposition behavior with oxygen release and their relationship to the thermal stability of the charged cathode material is very important.
In this regard, we have developed techniques using a combination of the in situ time-resolved X-ray diffraction (TR-XRD) and mass spectroscopy (MS) to monitor the structural changes and gas evolution during the thermal decomposition of charged cathode materials. In addition, in situ X-ray absorption spectroscopy (XAS) during heating has been also developed to look at the local and electronic structural changes occurring during thermal decomposition in an elemental selective way. By employing these combined in situ techniques, we are able to understand various aspects of the structural and electronic structure changes in the charged cathode materials during thermal decomposition; these include thermal decomposition paths, differences in phase-distribution, phase nucleation and propagation, the preferred atomic sites and migration paths of transition metal cations (Ni, Co, Mn, and Fe) and their individual contributions to thermal stability, together with measuring the oxygen release that accompanies these structural changes during heating. In this talk, several case studies on various cathode materials including layer-structured LiNixMnyCozO2 and high-voltage spinel LiNi0.5Mn1.5O4 will be covered. These results will provide valuable guidance for developing new cathode materials with improved safety characteristics.
The work done at Brookhaven National Lab. was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. DOE under Contract No. DE-AC02-98CH10886. K. N. was supported by the Dongguk University Research Fund of 2014.
YY1: Soft X-Ray In Situ Probes---Ambient Pressure XPS and Related Techniques I
Tuesday AM, April 07, 2015
Marriott Marquis, Yerba Buena Level, Nob Hill A/B
9:30 AM - *YY1.01
Heterogeneous Chemistry of Aqueous Interfaces Investigated under Ambient Conditions
Hendrik Bluhm 1
1Lawrence Berkeley National Laboratory Berkeley United StatesShow Abstract
The heterogeneous chemistry of solid/vapor, solid/liquid, and liquid/vapor interfaces governs many processes in catalysis, electrochemistry, and the environment. Examples include the removal of harmful components from automotive exhaust streams, heterogeneous reactions at the electrodes of solid oxide fuel cells, cloud droplet nucleation on atmospheric aerosols particles, as well as the uptake and release of trace gases by the polar snowpack. The prospects for a fundamental understanding of the basic reaction mechanisms at these interfaces on the molecular scale and under realistic operating conditions have greatly improved over the past decades through the development of in situ surface science methods, among them ambient pressure photoelectron and near edge X-ray absorption spectroscopy. This talk will discuss the application of these techniques to studies of the reaction of water vapor with oxide surfaces as well as new strategies for measuring liquid/solid interfaces by means of photoelectron spectroscopy.
10:00 AM - YY1.02
Probing Metal Organic Framework Thin Films for Gas Separation Using Ambient Pressure Photoemission Spectroscopy
Nour Nijem 1 May Ng 3 Stephen R. Leone 1 Mary K. Gilles 2
1University of California, Berkeley Berkeley United States2Lawrence Berkeley National Lab Berkeley United States3SLAC San Jose United StatesShow Abstract
Metal Organic Frameworks have emerged in applications related to gas separation and storage, sensing, and optoelectronic devices. In this work, HKUST-1 (also known as Cu2(BTC)3, BTC=1,3,5-Benzenetricarboxylate) MOF thin films are interrogated for co-adsorption of gases using Ambient Pressure Photoemission Spectroscopy (APPES) at the Advanced Light Source. The competitive adsorption between water and nitric oxide or water and ammonia are examined. APPES provides information about changes in metal center oxidation state, the bonding configuration of adsorbate, and binding strengths. Changes in the metal center oxidation state lead to differences in adsorption behavior. We find that NO adsorbs more strongly to photo-reduced Cu1+ as compared to Cu2+ in the presence of water. This highlights the potential of MOFs with lower oxidation state metal centers for selective adsorption of gases in the presence of water. Degradation of HKUST-1 in the presence of water and results from the bonding of ammonia to the unsaturated metal center that weakens the copper-ligand bond. This weakened copper-ligand bond enables water to replace the ligand, ultimately degrading the MOF.
 Nijem et. al. Chem. Comm., 2014, 50 (70), 10144 - 10147
10:15 AM - *YY1.03
In-Situ X-Ray Spectroscopic Investigations of CO2 Capture Materials
David Edward Starr 1
1Helmholtz-Zentrum Berlin Berlin GermanyShow Abstract
Fossil-fuel power plants are among the largest CO2 emission sources accounting for approximately one-third of anthropogenic CO2 emission. Due to increasing energy demands and slow deployment of clean energy alternatives, a practical near term route to CO2 mitigation is through CO2 capture and utilization. Currently, CO2 capture from power plants is typically done using aqueous solutions of monoethanolamine (MEA). We have used in-situ X-ray spectroscopic methods including ambient pressure X-ray photoelectron spectroscopy (AP-XPS) and resonant inelastic X-ray scattering (RIXS) to monitor CO2 uptake by thirty weight percent aqueous solutions of MEA, a standard concentration used in industry. Disadvantages of using aqueous MEA solutions include: high costs for regenerating the MEA solution after CO2 capture, solution degradation by flue gases like NOx and SOx, and equipment corrosion by the MEA solution. As a result, solid supported capture materials are being investigated as alternatives to aqueous MEA solutions for CO2 capture. We have used a model system approach to provide a molecular-level understanding of solid supported CO2 capture materials. We studied the adsorption of MEA on rutile TiO2(100) surfaces with complementary surface science methods, including synchrotron based X-ray photoelectron spectroscopy (XPS), Near Edge X-ray Adsorption Fine Structure (NEXAFS) and Scanning Tunneling Microscopy (STM), and Density Functional Theory (DFT) calculations and investigated its potential for CO2 capture with AP- XPS. By correlating this system&’s CO2 capture capabilities with an understanding of the bonding of MEA to the TiO2(110) surface a structure-property relationship was established. This allowed the development of an improved model solid-supported CO2 capture material based on monopropanol amine (MPA) adsorbed on TiO2(110).
YY2: Soft X-Ray In Situ Probes---Ambient Pressure XPS and Related Techniques II
Tuesday AM, April 07, 2015
Marriott Marquis, Yerba Buena Level, Nob Hill A/B
11:15 AM - *YY2.01
Combining In-Situ and Ex-Situ Techniques to Study Li Insertion and Ag Extrusion in Ag2VO2PO4
Ruibo Zhang 1 Linda Wangoh 1 Nicholas F Quackenbush 1 David C Bock 2 Matthew Huie 2 Tesfaye Abtew 3 Peihong Zhang 3 Amy Marschilok 2 Esther Takeuchi 2 Kenneth Takeuchi 2 M Stanley Whittingham 1 Louis Frederick Piper 1
1Binghamton University, SUNY Binghamton United States2Stony Brook University Stony Brook United States3The State University of New York at Buffalo Buffalo United StatesShow Abstract
Ag2VO2PO4 presents an interesting material to validate recent design principles for developing higher energy density lithium ion battery (LIB) cathodes without compromising safety. In particular, the combination of multiple readily accessible vanadium charge states (V5+, V4+, V3+), chemically stable PO43- groups, and the formation of a conductive Ag0 network during the lithium insertion are considered to be responsible for Li/Ag2VO2PO4 batteries demonstrating 205 mA h g-1 to 2.0 V and 270 mA h g-1 to 1.5 V. Detailed understanding of the reactions occurring in this system requires the use of computational studies, such as density functional theory (DFT) based electronic structure calculations and molecular dynamics (MD) simulations. The experimental knowledge regarding the evolution of the Ag and V coordination environments during the lithiation needs to be augmented to critically examine the results from DFT and MD. The use of traditional x-ray diffraction techniques to study the structural and chemical environment is not suitable for studying Li/Ag2VO2PO4 because of the loss of sharp Bragg peaks during the electrochemical discharge process. Instead, local probes of the evolution of the structural and chemical environments are required that do not rely upon long-range order. Here, we present our results combining in-situ pairs distribution function (PDF) measurements with ex-situ soft x-ray photoelectron spectroscopy (XPS) and near-edge x-ray absorption fine structure (NEXAFS) of carefully disassembled cells. The in-situ PDF monitored the evolution of the local structure, whilst ex-situ XPS and V L3,2-edge NEXAFS tracked the reduction of the Ag and V ions. We will compare our experimental findings to results from DFT and MD computations. This research was funded by a Network of Excellence grant from the Research Foundation of the State University of New York.
11:45 AM - YY2.02
Dissociative Adsorption of Water at the Surface of LaAlO3/SrTiO3 (100) Heterostructures
Yanwu Xie 1 2 Sarp Kaya 3
1Stanford University Stanford United States2SLAC National Accelerator Laboratory Menlo Park United States3SLAC National Accelerator Laboratory Menlo Park United StatesShow Abstract
Yanwu Xie,1,2 Sarp Kaya,3,4 Hirohito Ogasawara,3,4 Makoto Minohara,2 Yasuyuki Hikita,2 Christopher Bell,2 Anders Nilsson,3,4 Harold. Y. Hwang1,2
1Geballe Laboratory for Advanced Materials, Department of Applied Physics, Stanford University, Stanford, California 94305, USA
2Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
3SUNCAT Center for Interface Science and Catalysis, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
4Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
An important concept in designing oxide electronics is creating functional interfaces. A good example is the LaAlO3/SrTiO3 (100) heterostructure, which is known for its emergent conducting interface between the two band insulators . From an ionic viewpoint, along the (100) direction, LaAlO3 can be viewed as alternate stacking of positive (La3+O2-)1+ and negative (Al3+O24-)1- atomic layers, and thus the heterostructure has a polar LaAlO3 surface . Since polar oxides are extremely susceptible to ambient water vapor, it is of fundamental interest to understand how their surfaces interact with water and consequently affect proximate functional interfaces. In a recent experimental study  we have shown that the electronic conductivity at the LaAlO3/SrTiO3 interface can be strongly modulated by the exposure to water. However, a microscopic understanding of the change was lacking. In this work, using ambient pressure synchrotron X-ray photoemission spectroscopy, we studied the adsorption of water at the surface of the LaAlO3 /SrTiO3 (100) heterostructure. The samples were prepared by depositing LaAlO3 thin film on SrTiO3 (100) single-crystal substrate using pulsed laser deposition technique. Our results show that, upon increasing the water vapor pressure P from ultra-high vacuum to 1 Torr, water firstly adsorbs dissociatively at surface defects of the AlO2-terminated LaAlO3 (001) surface ( P < 10-4 Torr), and then dissociates at surface Al atoms until saturation with a monolayer of hydroxyl (10-4 Torr < P < 5×10-2 Torr), while the molecular water is largely adsorbed on top of the hydroxyl groups. The hydroxylation of the LaAlO3 (001) surface leads to a downward band bending up to 0.7 eV across the LaAlO3 film, suggesting an electron transfer from the surface to the interface.
This work is supported by the Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-AC02-76SF00515. Y.X. also acknowledges partial funding from the AFOSR-MURI on “Quantum Preservation, Simulation & Transfer in Oxide Nanostructures”.
 A. Ohtomo & H. Y. Hwang, Nature427, 423 (2004).
 N. Nakagawa et al., Nat. Mater.5, 204 (2006).
 Y. Xie et al., Nat. Commun. 2, 494 (2011).
12:00 PM - *YY2.03
The Catalytic Power of Oxide/Metal Interfaces Determined by In-Situ Studies
Dario J Stacchiola 1
1Brookhaven National Laboratory Upton United StatesShow Abstract
The traditional approach to the optimization of metal/oxide catalysts has focused on the properties of the metal phase. A low concentration of chemically active sites in the oxide support may be blocked by the anchoring of metal nanoparticles. By using a second oxide as a support (host), one can create a multifunctional con#64257;guration in which both metal and oxide nanoparticles are exposed to the reactants . As an example, depositing ceria on TiO2(110) leads to the formation of ceria dimmers . Atoms with properties ranging from metallic to ionic are available at the metal-oxide interface and create unique reaction sites. We show the creation of an efficient pathway for the water-gas shift reaction at the oxide-metal interface of ceria nanoparticles deposited on Cu(111) or Au(111). In situ experiments demonstrated that a carboxy species formed at the interface is the critical intermediate in the reaction . Our studies point to a new paradigm in the design of catalysts: The optimization of the oxide phase and the metal-oxide interface in a catalyst can improve substantially its activity and selectivity. Using this knowledge, we show have to create a new multifunctional active site for the conversion of CO2 to methanol.
 Chem. Rev 113, 4373-4390 (2013)
 Angew. Chem. Int. Ed. 52, 5101-5105 (2013)
 Science, 345, 546-550 (2014)
12:30 PM - YY2.04
Assessment of Proton-Phonon Coupling in Ceramic Electrolytes by (p,T)-Parameterization
Artur Braun 1 Qianli Chen 1 2 Jan P Embs 3 Stuart Holdsworth 1
1EMPA Duebendorf Switzerland2ETH Zuuml;rich Zuuml;rich Switzerland3Paul Scherrer Institut Villigen SwitzerlandShow Abstract
Super-protonic conductivity is a highly-wished-for functionality of solid electrolytes for intermediate temperature ceramic fuel cells and steam electrolyzers. Yttrium-substituted barium cerate and barium zirconate (BZY, BCY) - conventional ABO3-type ceramics with perovskite structure, are well-studied candidates for this purpose.
We have investigated the functional oxygen vacancy filling of engineered oxygen deficient BCY/BZY by water molecules with electro-analytical methods and ambient pressure XPS , which enabled to sketch a detailed picture of the correlation of molecular and electronic structure changes, and the concomitant onset of proton conductivity at elevated temperatures.
With this information we were able to design experiments, where the proton phonon coupling could be quantitatively investigated with high pressure-high temperature electrochemical impedance spectroscopy combined with quasi-elastic neutron scattering [2,3]. Supported with pressure dependent XRD and Raman scattering data [4,5] we were able to correlate the proton jumping parameters with the temperature and found that the proton jump times follow a Holstein polaron relation [6-9].
 Q. Chen et al., Chem. Mater. 25 (23), 4690 (2013).
 Q. Chen et al., Solid State Ionics 252, 2 (2013).
 Q. Chen et al., High Pressure Research 32(4), 471 (2012).
 Q. Chen et al., J. Phys. Chem. C 115 (48), 24021 (2011).
 Q. Chen et al., J. Eur. Ceram. Soc. 31 (14), 2657 (2011).
 Q. Chen et al., Appl. Phys. Lett. 97, 041902 (2010)
 A. Braun et al., Appl. Phys. Lett., 95, 224103 (2009).
 Q. Chen, Effects of Pressure on the Proton-Phonon Coupling in Metal Oxides with
Perovskite Structure, Diss., Eidgenössische Technische Hochschule ETH Zürich, Nr. 20554, 2012
 A. Braun, Q. Chen, Experimental evidence for the proton polaron in
metal oxide hydrates, submitted for publication.
Faisal Alamgir, Georgia Institute of Technology
Dario Arena, Brookhaven National Laboratory
John Baniecki, Fujitsu Laboratories
William C. Chueh, Stanford Univeristy
Gyula Eres, Oak Ridge National Laboratory
YY7: Designing Functionality: Theory and Experiment
Wednesday PM, April 08, 2015
Marriott Marquis, Yerba Buena Level, Nob Hill A/B
2:30 AM - *YY7.01
The Affair of the 'Missing Compounds': Theoretical Identification and Experimental Realization of Previously Overlooked Materials
Alex Zunger 1
1University of Colorado, Boulder Boulder United StatesShow Abstract
Materials have traditionally been introduced into technology either by incremental improvements on long-known substances (Si, CIS, CdTe, In2O3) or via chemical substitution of known materials or by serendipity. This time-honored tradition leaves out the possibility of yet undiscovered but potentially useful materials. Inspection of databases of all inorganic materials previously made (ICSD or ICDD) reveals that a few thousands are simply missing. These are combinations of chemical elements that are analogous to those appearing listed compounds but represent unreported compounds. One wonders if they are missing for a good reason (such as some inherent instability), or the community has simply not gotten around to try and make them, yet they might be interesting. Systematic laboratory synthesis of all such candidate-missing materials would seem a horrendous project. A possible alternative is to perform initial screening of hundreds of Missing Compounds by using first-principles thermodynamics, and then attempt laboratory realization of narrower lists of missing materials. I will describe in this talk the basic idea behind First Principles Quantum Thermodynamics leading to the prediction of scores of previously missed A2BX4 chalcogenides as well as ABX 1:1:1 compounds such as the 18 electron III-X-V ;II-X-VI; IV-X-IV; V-IX-IV; and IV-IX-V groups. Synthesis efforts by three synthesis teams —the Northwestern Mason group, and Poeppelmeir group, the OSU Keszler group -will be described.
3:00 AM - *YY7.02
Big, Deep, and Smart Data in Energy Materials Research: Atomic View on Materials Functionalities
Sergei V. Kalinin 1
1Oak Ridge National Laboratory Oak Ridge United StatesShow Abstract
The development of electron and scanning probe microscopies in the second half of XX century have produced spectacular images of internal structure and composition of matter with nanometer and now atomic resolution. Much of this progress since 80ies was enabled by computer-assisted methods for data acquisition and analysis that provided automated analogs of classical storage methods. However, the progress in imaging technologies since the beginning of XXI century has opened the veritable floodgates of high-veracity information on atomic positions and functionality, often in the form of multidimensional data sets containing partial or full information on atomic positions, functionalities, etc. In this presentation, I will discuss several examples of high-resolution studies of the structural, electronic and electrochemical properties of oxide surfaces enabled by multidimensional scanning probe microscopies synergistically combined with the big data technologies. On the mesoscopic scale, combination of strain- and current sensitive scanning probe microscopies allows to build nanometer-scale maps of local reversible and irreversible electrochemical activities. The use of multivariate statistical methods allows separating the complex multidimensional data sets into statistically significant components which in certain cases can be mapped onto individual physical mechanisms. I will further discuss the use of in-situ Pulsed Laser Deposition growth combined with atomic resolution Scanning Tunneling Microscopy and Spectroscopy to explore surface structures and electrochemical reactivity of oxides on the atomic scale. For SrRuO3, we directly observe multiple surface reconstructions and link these to the metal-insulator transitions as ascertained by UPS methods. On LaxCa1-xMnO3, we demonstrate strong termination dependence of electronic properties and presence of disordered oxygen ad-atoms. The growth dynamics and surface terminations of these films are discussed, along with single-atom electrochemistry experiments performed by STM. Finally, I explore the opportunities for atomically-resolved imaging and property data mining of functional oxides extending beyond classical order parameter descriptions, and giving rise to the deep data analysis in materials research.
This research is supported by the by the U.S. Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division, and was conducted at the Center for Nanophase Materials Sciences, which is sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, BES DOE.
3:30 AM - *YY7.03
Modeling of Materials, What Can and Canrsquo;t be Done
Olle Eriksson 1
1Uppsala University Uppsala SwedenShow Abstract
In this presentation I will make a short review of the basic ideas behind electronic structure theory, leading both to the ‘conventional&’ description of essentially non-correlated electronic structures, as well as to correlated electron systems where dynamical mean field theory is an important recently developed tool. Examples of how these theories perform in reproducing materials will be primarily given from the group of magnetic compounds, where recent energy relevant applications concern e.g. magnetocalorics and rare-earth free permanent magnets. Special attention will be given to the dynamics of magnetic materials, using an atomistic spin-dynamics method that is coupled to electronic structure theory via a multi-scale approach.
YY8: In Situ Measurements Using Neutrons
Wednesday PM, April 08, 2015
Marriott Marquis, Yerba Buena Level, Nob Hill A/B
4:30 AM - *YY8.01
In Operando Neutron Measurements of Lithium Ion Batteries
Howard Wang 1
1State University of New York, Binghamton Binghamton United StatesShow Abstract
Rechargeable Li-ion batteries (LIB) are a promising technology for efficient energy storage. We have carried out critical in operando neutron measurements on Li distribution and transport to gain new insights in the function and failure of battery systems. Four neutron measurement techniques, neutron depth profiling (NDP), neutron reflectivity (NR), small angle neutron scattering (SANS), and neutron imaging (NI) have been used to quantify real-time information of the Li transport in electrode, sub-nanometer thin film and interfacial structures, and fracturing of electrode particles. NDP data show that a true measure of the Coulombic efficiency requires the quantification of both ionic and electric charge displacements in a single trip and the discrepancy between the ionic and electric transport is a powerful indicator of the onset of battery failure. Tomographic 3D NDP helps map lithium distribution in electrodes to indicate spatial heterogeneities of lithium in cathodes that had undergone different electrochemical cycling histories. NR probes depth-dependent compositions and interfacial structures in buried thin films with sub-nanometer resolution and correlates the lithiation state with the integrity of electrode films. Using a thin amouphouse silicon film having undergone lithiation and delithiation cycles, in operando NR reveals that a “pore collapse and regrowth” mechanism is responsible for highly reversible cycling of the nanoscale slicon anode. Quantitative analysis of in-situ SANS data yields the total area of fracture surfaces of graphite particles induced by lithiation/delithiation cycling. The information could be used to relate the capacity decay to the usable cycle life of LIBs. Real-time NI monitoring of the lithiation of highly-oriented pyrolitic graphite illustrates the existence of hot-spots near the surface, through which Li ions enter to intercalate the bulk of the graphite electrode. The findings demonstrate that in situ neutron measurements offer promising new opportunities for better understanding of rechargeable batteries.
5:00 AM - YY8.02
In situ Characterisation of Energy Materials at the ISIS Pulsed Neutron Source
Martin Owen Jones 1 Jon Hartley 4 1 George Carins 2 Josh Makepeace 3 1 John Irvine 2 Adrian Porch 4 William I. F. David 1 3
1STFC Didcot United Kingdom2Univ of St Andrews St Andrews United Kingdom3Oxford University Oxford United Kingdom4Cardiff University Cardiff United KingdomShow Abstract
The study of energy materials forms a significant proportion of the research carried out on the ISIS pulsed neutron spallation source, part of the Rutherford Appleton Laboratory campus, the UK&’s largest national laboratory. In order to study the functional properties of interest we often must commission new sample environment apparatus so that these properties may be investigated simultaneously with material structure or molecular dynamics. Furthermore, these apparatuses commonly must be able to operate at elevated temperatures and pressures, under gas flow or in vacuum and work with corrosive, air-sensitive or toxic chemicals. Experiments that comprise simultaneous, multi-technique characterisation in functionally significant conditions are termed ‘in-operando&’, and here I describe the development of 3 such systems.
A microwave resonator for simultaneous dielectric, structural and mass spectroscopy characterisation of solids during ammonia gas uptake at room temperature.
Simultaneous ionic conductivity and structural characterisation at high temperature under hydrogen atmospheres.
In-operando decomposition of ammonia gas over Li2NH catalysis at high temperature and under gas flow.
This presentation will include details of apparatus design and commissioning, together with recent in-operando experimental results from all three systems. The insights gained from the in-operando experimental methodology will be highlighted.
5:15 AM - YY8.03
Operando Neutron Diffraction Studies of Li-Ion Battery Electrodes
Matteo Bianchini 1 2 3 Emmanuelle Suard 1 Laurence Croguennec 3 Christian Masquelier 2
1Institut Laue Langevin Grenoble France2Laboratoire de Reactiviteacute; et de Chimie des Solides Amiens France3Institut de la Chimie et de la Matiere Condenseacute;e Bordeaux FranceShow Abstract
In-situ techniques proved to be exceptionally useful tools to understand electrode materials for Li-ion batteries. Despite the great interest generated by neutrons&’ sensitivity to lithium, in-situ neutron diffraction (ND) knew a slow development due to the intrinsic difficulties it held. We recently designed an electrochemical cell manufactured with a completely neutron-transparent (Ti,Zr) alloy. Used with deuterated electrolytes, the cell is able to combine good electrochemical properties and the ability to collect ND patterns operando, with good statistics and no other Bragg peaks than those of the electrode material of interest. Importantly, this allows detailed structural determinations by Rietveld refinement during operation. The cell was validated using well-known battery materials such as LiFePO4 (1) demonstrating real operando experiments conducted on the D20 high flux neutron powder diffractometer at ILL Grenoble,France. The cell was then used to study challenging materials. We report in particular on a series of spinel materials Li1+xMn2-xO4 (x=0, 0.05, 0.1). The well-known difference in electrochemical performances (capacity fading) observed in this family of materials was thoroughly investigated using operando neutron diffraction. We synthesized LiMn2O4, Li1.05Mn1.95O4 and Li1.10Mn1.90O4 and observed their charging process in real time. The study (2) showed that not only the volume change induced by the delithiation is reduced while going from LiMn2O4 to Li1.10Mn1.90O4, but more importantly that the mechanism by which this happens is modified. In fact, while Li1.10Mn1.90O4 reacts though a "simple" monophasic reaction (a solid solution), Li1.05Mn1.95O4 shows the existence of a solid solution process followed by a biphasic reaction and LiMn2O4 even shows a sequence of two biphasic reactions. Both the above mentioned features contribute to make overlithiated Li1.10Mn1.90O4 a much better candidate for use in Li-ion batteries than the standard stoichiometric LiMn2O4. In more details, neutrons allow us to be sensitive to lithium&’s atomic parameters, such as atomic coordinates and even site occupancy factors (SOFs), and thus to include them in our Rietveld analysis to increase the accuracy of our time-dependent structural model. In the specific case of Li1+xMn2-xO4 spinels this meant the possibility to correlate, for the first time, the evolution of lithium&’s SOF with the electrochemical features of the materials, which is of key importance for understanding and therefore improving Li-ion battery materials. Moreover, the cell will be used for several in-situ experiments in late 2014 (Mn and (Mn,Ni) spinels (dis)charge), not only using standard neutron diffraction, but also to develop in-situ Neutron Pair Distribution Function analysis. The first results of these experiments will be reported. Ref: (1) M. Bianchini et al., J. Electrochem. Soc., 160 (2013), A2176. (2) M. Bianchini et al., J. Phys. Chem. C (2014) accepted, DOI:10.1021/jp509027g.
5:30 AM - YY8.04
CO2 Adsorption-Induced Pore Deformation in Nanoporous Carbon
Jitendra Bahadur 1 Yuri Melnichenko 1 Cristian Contescu 2 Nidia Gallego 2
1Oak Ridge National Laboratory Oak Ridge United States2Oak Ridge National Laboratory Oak Ridge United StatesShow Abstract
In-situ Small-angle neutron scattering (SANS) was used to study adsorption of carbon dioxide (CO2) in the porous carbon. The pore size distribution of the studied carbon is bimodal, with the average size of the mesopores and nanopores ~ 20 Å and 5 Å, respectively. The adsorption behavior of CO2 in both meso- and nanopores was probed by measuring SANS intensity from CO2-saturated sample as a function of relative pressure P/P0 in the range of 0.0 to 0.85 at temperature T= 23oC. The density of the confined CO2 was estimated by analyzing Porod invariant at different P/P0. Significant densification of CO2 was observed in the nanopores, in which the density of the adsorbed fluid (ρCO2 ~ 1 g/cc) exceeded by a factor of ~ 15 the density of bulk CO2 at the same pressure and temperature. The fluid densification in the mesopores is negligibly small as compared to densification in the nanopores. The CO2 mass uptake at different pressures measured by SANS agrees with independent gas adsorption experiments. The pore size distribution of nanopores is pressure dependent: the average size of the pore increases initially with pressure and then starts decreasing at pressure P/P0=0.25. In order to delineate the effect of hydrostatic pressure on the pore deformation, SANS experiments have been carried out using non-adsorbing fluid (Argon). It was found that SANS profiles remain unchanged with pressure indicating that the pore structure is not affected by the hydrostatic pressure. We tentatively assign the observed deformation of the nanopore to the strong interaction potential between pore wall and CO2 molecules.
5:45 AM - YY8.05
Neutron Imaging of Hydrogen Isotope Separation Columns
George M. Buffleben 1 Andrew D. Shugard 1 David B. Robinson 1 David L. Jacobson 2 Daniel S. Hussey 2 Eli Baltic 2
1Sandia National Laboratories Livermore United States2National Institute of Standards and Technology Gaithersburg United StatesShow Abstract
Hydrogen isotopes must be purified in nuclear energy applications, either to minimize environmental release of tritium from fission reactors, to reduce 1H contamination in heavy water reactors, or to prepare appropriate gas mixtures for nuclear fusion experiments. An especially effective category of isotope separation methods uses the strong isotopic dependence of the equilibrium between gas-phase hydrogen and condensed-phase hydrogen compounds. Palladium is a notable sorbent material for this purpose because it can reversibly form hydrides at near-ambient temperatures and pressures. To design an effective separation system, the behavior of the sorbent material should be well understood.
One way to evaluate the isotope separation performance of a solid hydride is through a configuration similar to gas chromatography. In this experiment, a sorbent material is packed into a tube, and loaded with a given hydrogen isotope. Another isotope is then introduced at one end of the tube, and the outlet gas composition is monitored at the other end by mass or Raman spectrometry. Under certain operating conditions, the chemical rate constants for the exchange of isotopes between the gas and solid phase can be derived. To improve confidence that these operating conditions are actually present, we have performed neutron imaging experiments that allow us to observe the location of 1H throughout the column during an entire experiment, from when it first enters until it passes all the way through. The experiments reveal how a hydrogen-deuterium boundary responds to suboptimal flow conditions and to defects in a column, and also how the boundary evolves when more desirable conditions are restored. Our results have provided important insights into the interpretation of isotope exchange chromatography experiments that will aid future development of this category of separation technologies.
This work was supported by the Laboratory-Directed Research and Development program at Sandia National Laboratories, a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. The work was also supported by the U.S. Department of Commerce, the NIST Radiation and Physics Division, the Director's office of NIST, the NIST Center for Neutron Research, and the Department of Energy interagency agreement No. DE_AI01-01EE50660. SAND2014-18899 A
 Vasaru, G. Tritium Isotope Separation. CRC Press, 1993.
 Heung, L. K.; Sessions, H. T.; Poore, A. S.; Jacobs, W. D.; Williams, C. S. “Next-generation TCAP hydrogen isotope separation process.” Fusion Sci. Tech. 54 (2) 399-402, 2008.
 Foltz, G.W.; Melius, C.F. Studies of Isotopic Exchange Between Gaseous Hydrogen and Palladium Hydride Powder, J. Catalysis 108 409-425 (1987)
YY9: Poster Session
William C. Chueh
Wednesday PM, April 08, 2015
Marriott Marquis, Yerba Buena Level, Salon 7/8/9
9:00 AM - YY9.01
Enthalpies of Water Uptake of Yttrium-Doped Barium Zirconate Solid Solutions Measured by Water Adsorption Calorimetry
Mayra Dancini Gonccedil;alves 1 3 Aleksandra Mielewczyk-Gryn 3 2 Sergey Ushakov 3 Alexandra Navrotsky 3 Reginaldo Muccillo 1
1Energy and Nuclear Research Institute Sao Paulo Brazil2Gda#324;sk University of Technology Gda#324;sk Poland3University of California Davis United StatesShow Abstract
The proton conductor yttrium-doped barium zirconate, BaZr1-xYxO3-δ (BZYx), has emerged as a promising material to be applied as an electrolyte in intermediate temperature (400 - 700 oC) solid oxide fuel cells (IT-SOFCs). The special interest on this material is due to its relatively high proton conductivity and chemical stability in CO2 containing atmospheres. Therefore, the BZYx defect chemistry and the hydration characteristics must be fully characterized and understood prior to using this material in electrochemical devices. In the present work, the BZYx (x = 10, 20 and 30 mol% Y) hydration behavior was investigated for the first time using water adsorption calorimetry technique. A surface area analyzer with water vapor dosing system coupled with a Calvet-type microcalorimeter is used. Such system configuration allows precise dosing of water and in-situ measurement of adsorption enthalpies (ΔHads) using a relatively small amount of sample . The experiment was performed from 25 to 600 oC aiming to obtain the enthalpy of bulk hydration (oxygen vacancies filling) as a function of dopant content and temperature. The BZYx powders were synthesized by the oxidant-peroxo method and heat treated at 1200 oC for 24 h . The samples were characterized by electron microprobe, X-ray diffraction, thermogravimetry, infrared spectroscopy and surface area (BET) analyses. The water adsorption experiment was programmed in an incremental dose mode to provide 10 mu;mol of H2O up to the equilibration pressure (~ 0.021 atm). The quantity of adsorbed water is higher when the content of dopant increases in the BZYx solid solutions from x= 0.1 to 0.3. The enthalpies of adsorption are found to be exothermic for all compositions and reach more exothermic values when the dopant increases from x = 0.1 to 0.2. From x = 0.2 to 0.3 there is only a small exothermic increment to the enthalpy of adsorption at 300 and 400 oC. The results indicate that defect clustering and defect association (Y partitioning among A and B sites) should have a contribution on decreasing the density of available oxygen vacancies with increasing the dopant content from BZY0.2 to BZY0.3 .
 S. Ushakov, A. Navrotsky, Appl. Phys. Lett. 87 (2005) 164103.
 M.D. Gonccedil;alves, R. Muccillo, Ceram. Int.40 (2014) 911-917.
 M.D. Gonccedil;alves, P.S. Maram, R. Muccillo, A. Navrotsky, J. Mater. Chem. A 2 (2014) 17840.
9:00 AM - YY9.02
In Situ TEM Study of Electrical Wind Force-Driven Amorphization in Phase-Change Materials
Sung-Wook Nam 1
1University of Pennsylvania Philadelphia United StatesShow Abstract
Electrical wind force is an important element in electrical switching behaviors of phase-change materials. It has been reported that the electrical wind force influences the motions of dislocations, which determines the degree of order-disorder states existing in phase-change materials . In this presentation, we discuss electrical wind force-driven behaviors occurring in phase-change materials. At first, we report atomic mass-transport behaviors as DC voltage biases are applied in line-shape Ge2Sb2Te5 (GST) devices. As the electrical current density reached 3-4 MA/cm2 by DC voltage bias, a directional mass transport was identified by forming asymmetric surface morphology on the line-shape GST devices. By electric current, Joule-heating raised the temperature up to ~300 oC, implying that the mass transport of GST occurs in hexagonal phase (solid state) regime. In second, we extend the roles of electrical wind force to electrical switching behaviors of GST. We studied the effects of electrical voltage pulses on crystalline-to-amorphous phase transition of GST by in situ transmission electron microscopy (TEM). Electrical voltage pulse plays a critical role by creating dislocations through heat shock process: Rising edge of the pulse produces vacancies by heating, whereas during rapid cooling, atomic vacancies are condensed into dislocation loops. As the dislocations feel the electrical wind force, they become mobile and glide in the direction of hole-carrier motion. Continuous increase in the density of dislocations moving unidirectionally leads to dislocation jamming, which eventually induces the crystalline-to-amorphous phase transition. We interpret it through one-dimensional traffic model in which the increase of dislocation density exceeding a certain threshold point induces a catastrophic jamming of dislocations. Density functional theory (DFT) calculations of generalized-stacking-fault (GSF) energy show that basal plane of GST hexagonal phase provides favorable pathways of dislocation motions. Our understanding about dislocation-templated amorphization suggests that the transition from crystalline to amorphous states in phase-change materials may not require a melting process.
 S.W. Nam et al, Science, 336, 1561-1566 (2012)
9:00 AM - YY9.03
Electron Tomography and In Situ Electrical Characterization of Organic-Inorganic Hybrid Nanodielectrics
Ming-Siao Hsiao 1 3 Christopher Grabowski 1 3 Anmin Nie 2 4 Hasti Asayesh-Ardakani 2 4 Jacob S Kolar 2 4 Yifei Yuan 2 4 Reza Shahbazian-Yassar 2 4 Lawrence Drummy 1
1Materials and Manufacturing Directorate, Air Force Research Laboratory, WPAFB Dayton United States2Department of Mechanical Engineering, Michigan Technological University Houghton United States3UES, Inc Dayton United States4Physics Department, University of Illinois at Chicago Chicago United StatesShow Abstract
Polymer nanocomposites (PNCs) and polymer-grafted “hairy” nanoparticles (HNPs) are of current interest for a wide array of mechanical, thermal and electrical applications, including energy storage in high energy density capacitors. For these nanostructured soft materials to be engineered for optimized property combinations such as high relative permittivity and high electrical breakdown strength, a detailed structure-property relationship must be constructed which builds upon quantitative, three dimensional morphology information and in-situ property characterization. The advantages of in-situ characterization are that it provides direct characterization of the material during operation in the end use application, and it has the potential for capturing dynamical information. Additionally, transient phenomenon or narrow phase windows can be captured which are difficult to observe using ex-situ techniques. We have been investigating structure property relations of PNCs and HNPs (polystyrene-silica) using transmission electron tomography, three dimensional reconstruction, and in-situ electrical testing. Electron tomography reconstruction using Model-Based Iterative Reconstruction was able to resolve the individual oxide nanoparticles with nanometer resolution, and their distribution within the polymer matrix. In-situ characterization was performed using electrical testing chips to probe electric field ranges from 0.1-10 V/micron and an in-situ probe holder apply fields in the range of 10-500 V/micron. Dielectric breakdown at high fields was observed in-situ, at fields which were comparable to ex-situ measurements on bulk films, and several interesting phenomenon were observed in the in-situ experiments pre- and post-breakdown. In-situ analysis of the nanodielectric material post-breakdown revealed significant morphological changes and chemical changes, which were quantified using tomography and electron energy loss spectroscopy and compared with FIB lift out ex-situ experiments on bulk films.
9:00 AM - YY9.04
Operando TEM of Ru Catalysts for CO Oxidation
Benjamin K Miller 1 Peter A. Crozier 1
1Arizona State University Tempe United StatesShow Abstract
Linking catalyst structure with catalyst activity is a primary goal of much catalysis research. Observation of the catalyst structure at the atomic scale using environmental TEM (ETEM) while catalysis is taking place is a powerful technique for linking activity with structure. To do this well, it is essential to know the activity of the catalyst while it is being observed. This can be accomplished by measuring the gaseous products inside the ETEM using two complimentary techniques: electron energy loss spectroscopy (EELS) and residual gas analysis (RGA).
EELS and RGA both have advantages and drawbacks. EELS measures the gas immediately surrounding the sample, unlike the RGA, which is located some distance from the sample chamber, and must be differentially pumped. The RGA can monitor the gas composition continuously, even if there is no electron beam in the column, while EELS cannot be acquired at the same time as a TEM image. The RGA can detect smaller quantities of gas, while EELS is easier to quantify precisely.
We are applying the operando technique to determine structure-reactivity relations in Ru catalysts for CO oxidation. Though Ru for CO oxidation is a well-studied system, there is still debate in the literature regarding the most active state of the catalyst surface. Using a differentially pumped ETEM, the silica-sphere-supported Ru catalyst is initially either fully oxidized or reduced in-situ, and then heated in a stoichiometric mixture of CO and O2 to a temperature at which we observe high CO conversion. A unique sample preparation method was developed to increase the amount of catalyst inside a Gatan Ta heating holder, thus maximizing the amount of product gas formed. Experiments are performed on both an FEI Tecnai and FEI aberration-corrected Titan.
We have observed that initially oxidized particles (RuO2) have low activity even above 400oC. At high temperature, these particles are reduced in-situ by the CO-O2 reactant gas mixture and are subsequently more active for CO2 production, as the temperature is ramped back down. Additionally, the particle morphology observed when the catalyst is highly active is similar to that observed at the same temperature in pure CO gas. The morphology in O2 gas is markedly different, showing a Ru-core/RuO2-shell structure. This suggests that under reaction conditions, the gas adsorbates are predominately CO, not O2.
Aberration corrected microscopes dramatically increase the amount of detail observable on the surface of catalyst nanoparticles, but measures must be taken to keep particles as stable as possible during acquisition. Supports such as CeO2 which are stable under the beam and show a strong metal-support interaction should decrease the movement of the Ru catalyst particles, allowing detailed analysis of surface facets and edges.
 This work was supported by The National Science Foundation (NSF-CBET 1134464).
9:00 AM - YY9.05
In-Situ Detection of Hydrogen-Induced Phase Transitions in Individual Palladium Nanocrystals
Andrea Baldi 1 Tarun Chandru Narayan 1 Ai Leen Koh 1 Jennifer Dionne 1
1Stanford University Stanford United StatesShow Abstract
Many energy and information storage processes, such as hydrogen storage, battery charging, and memory switching, rely on phase changes of nanostructured materials in reactive environments. Compared to their bulk counterparts, nanostructured materials appear to exhibit faster charging and discharging kinetics, an extended life cycle, and size-tunable thermodynamics.
However, in ensemble studies of these materials, it is often difficult to discriminate between intrinsic size-dependent properties and effects due to sample size and shape dispersity. Studies of hydrogen absorption in individual nanoparticles so far have been limited to nanostructures evaporated onto a substrate or to thin shells grown on a nanoscale core. In all these cases, however, there is limited control over the sample size and shape and the thermodynamics of hydrogen absorption is heavily influenced by the elastic interaction of the particle with the support.
Here, we present the first direct measurement of hydrogen absorption and desorption in individual colloidally-synthesized palladium nanocrystals, with sizes ranging from 29 nm down to 13 nm . Our approach is based on in-situ electron energy-loss spectroscopy (EELS) in an environmental (scanning) transmission electron microscope.
By measuring the spectral position of the bulk plasmon resonance of individual palladium nanoparticles while varying the hydrogen pressure, we construct single-particle pressure - energy-loss isotherms. In contrast to ensemble measurements, in which sloped H2 loading/unloading isotherms are observed , we find that palladium nanocrystals undergo sharp transitions between the α and β phases, with smaller particles loading at lower hydrogen pressures.
The observed size-dependence of the loading pressures can be understood by taking into account the elastic stress induced by the preferential hydrogen absorption at the surface of the nanocrystals. Such a surface-induced mechanism is similar to the one suggested for the intercalation of lithium in FePO4 nanoparticles  and could be responsible for the mechanism of solute intercalation in a variety of nanostructured materials.
Our results provide a framework for the in-situ study of phase transitions in individual nanocrystals and highlight the importance of single-particle approaches for the characterization of nanostructured materials for energy storage.
 A. Baldi, T. C. Narayan, A. L. Koh and J. A. Dionne, Nature Materials AOP (2014)
 R. Bardhan et al., Nature Materials 12, 905-912 (2013)
 D. A. Cogswell and M. Z. Bazant, Nano Letters 13, 3036minus;3041 (2013)
9:00 AM - YY9.06
Using Atom Probe Tomography to Understand Photovoltaic Cells at Atomic Level
Mohit Raghuwanshi 2 Adeline Lanterne 1 Jerome Le Perchec 1 Philippe Pareige 2 Emmanuel Cadel 2 Samuel Gall 1 Sebastien Duguay 2
1CEA, LITEN Le Bourget du Lac France2Universiteacute; et INSA de Rouen Saint Etienne du Rouvray FranceShow Abstract
Photovoltaics is conversion of light into electricity which takes place at atomic level, to further enhance performance of photovoltaic cells it is necessary to probe cells at atomic level which is now possible using Atom Probe Tomography (APT). APT can resolve materials and provide 3D atomic information at sub-nanometer level. Here we use this technique to understand and enhance efficiency of Silicon and Copper Indium Gallium Selenide (CIGS) solar cells by probing them at atomic level.
Photovoltaic is currently dominated by Silicon solar cells, and using ion implantation doping instead of standard diffusion process is a promising way to simplify the fabrication of silicon solar cells. However difficulties to form high quality boron (B) implanted emitters are encountered when implantation doses suitable for the emitter formation are used. This is due to a more or less complete activation of Boron after thermal annealing. Here we explain using APT results how different doping conditions change B distribution in Si at atomic level and systematically changes its emitter saturation current density.
CIGS is currently the most efficient solar cell (efficiency > 20%) under thin film category. This high efficiency is obtained for polycrystalline CIGS due to Na atoms (diffused from the glass substrate) segregation along Grain Boundaries (GBs). This increased efficiency due to presence of GBs is both surprising and interesting; to understand the role of GBs in changing the electrical properties of CIGS advanced characterization techniques like APT must be used. Herein we combine EBSD (Electron Back Scattered Diffraction) to locate GBs and APT to explore nano-chemistry of GBs in CIGS for different Ga concentrated samples. Results show that: composition profile at GBs strongly depends on Ga ratio (Ga/In+Ga). Depletion and enrichment in Cu conc. is observed at GB for Ga poor and Ga rich samples respectively, suggesting different phase compositions at GBs for different Ga ratios. Efficiency variation of CIGS for different Ga concentration is linked for the first time with its GB composition profile will be discussed.
9:00 AM - YY9.08
Investigation of Grain Boundary Effects in Energy Storage Materials by Local Charge Transport Measurements
Michael Noyong 1 2 Shuo Yang 1 2 Felix Schrader 1 2 Ulrich Simon 1 2
1RWTH Aachen Aachen Germany2JARA Aachen GermanyShow Abstract
The understanding of energy storage materials properties is of great interest in academia and industries. The complex interplay of bulk and interface properties determines the overall properties, but it is still challenging to discriminate intrinsic grain from intergrain properties. Therefore, it would be highly desirable to probe the properties of individual grains, which are typically nanoscale building blocks in the context of its macroscopic environment or assembly. Hence, probing the charge transport e.g. of individual nanocrystals in a macrosized functional electrode or of individual nanowires in a 3D assembly would be of great interest.
In this work we demonstrate the feasibility of a highly flexible four-probe nanorobotics setup, which allows local charge transport measurements with high spatial resolution on real world samples under scanning-electron microscopic inspection. We will illustrate the effect of grain boundaries of different energy storage materials on the charge transport on nanostructured surfaces exhibiting nanocrystal domains.
9:00 AM - YY9.09
Local Crystallography: Phase Recognition and Local Symmetry Analysis
Alex Belianinov 1 Qian He 3 Oleg Ovchinnikov 1 Artem Maksov 1 Stephen Jesse 3 Albina Borisevich 3 Sergei V. Kalinin 2
1Oak Ridge National Lab Oak Ridge United States2Oak Ridge National Laboratory Oak Ridge United States3Oak Ridge National Laboratory Oak Ridge United StatesShow Abstract
With advances in high resolution imaging in (scanning) transmission electron microscopy and scanning probe microscopies, precision measurements (10 pm or better) of atomic positions are routinely obtained. This level of fidelity is sufficient to correlate bond length (and hence energy), as well as bond angle, to functional properties of materials. We introduce an approach for local analysis of material structure based on statistical analysis of individualized, local atomic neighborhoods. Both supervised and unsupervised learning algorithms are used; this allows for a highly flexible framework of specified metrics which in turn are sensitive various lattice aspects. Using the local neighborhood approach we demonstrate phase identification as well as unit cell identification and classification. Multiphase catalytic materials, complex oxides and 2D materials are presented as case studies. Furthermore approaches for building image genomes and structure-property libraries, based on conjoining structural and spectral realms through local atomic behavior are discussed.
9:00 AM - YY9.10
Mechanisms of Electrochemical Charge Storage in Two-Dimensional Ti3C2 MXene Studied by In-Situ EQCM
Maria R. Lukatskaya 1 Mikhael D. Levi 2 Doron Aurbach 2 Majid Beidaghi 1 Michel W Barsoum 1 Yury Gogotsi 1
1Drexel Univ Philadelphia United States2Bar-Ilan Univ Ramat-Gan IsraelShow Abstract
MXenes, a recently discovered large family of two-dimensional (2D) early transition metal carbides and carbonitrides, have shown much promise in electrochemical energy storage applications, such as battery and supercapacitor electrodes. We recently reported on large volumetric capacitance and high rate capabilitiy of Ti3C2Tx - the most studied MXene to date. Spontaneous intercalation of a variety of single- and multiply charged cations, together with highly reversible electrochemical insertion of the same cations, has been well documented for Ti3C2Tx in aqueous electrolytes. Perfect capacitive behavior was observed for Ti3C2Tx MXene even at quite high charge and discharge rates, contradicting to slow intercalation of ions in a specific potential range, which is usually observed in layered materials for battery applications.
In order to understand mechanism of capacitance in MXenes we performed characterization of the mechanical deformations of MXene electrode materials at various states-of-charge with a variety of cations (Li, Na, K, Cs, Mg, Ca, Ba, and three tetrashy;alkylammonium cations) during cycling by electrochemical quartz-crystal admittance (EQCA, quartz-crystal microbalance with dissipation monitoring) combined with in situ electronic conductance and electrochemical impedance. Based on this work, it appears that in MXenes cationic insertion is accompanied by significant deformation of the Ti3C2Tx particles, that occurs so rapidly so as to resemble 2D ion adsorption at solid-liquid interfaces. The latter is greatly facilitated by the presence of water molecules between the MXene sheets.
M. R. Lukatskaya, O. Mashtalir, C.E. Ren, Y. Dall&’Agnese, P. Rozier, P. L. Taberna, M. Naguib, P. Simon, M.W. Barsoum, Y. Gogotsi, “Cation Intercalation and High Volumetric Capacib tance of Two-dimensional Titanium Carbide” Science, 2013, 341 (6153), pp. 1502-1505
M. D. Levi, M. R. Lukatskaya, S. Sigalov, M. Beidaghi, N. Shpigel, L. Daikhin, D. Aurbach, M. W. Barsoum, Y. Gogotsi, “Solving the Capacitive Paradox of 2D MXene by Electrochemical Quartz-Crystal Admittance and in situ Electronic Conductance Measurements” Advanced Energy Materials, DOI: 10.1002/aenm.201400815
9:00 AM - YY9.11
In-Situ High-Energy Synchrotron X-Ray Diffraction and Atomic Pair Distribution Function Studies on Binary and Ternary Nanoalloy Catalysts at the Cathode of PEMFCs
Valeri Petkov 1
1Dept. Physics, Central Michigan University Mt Pleasant United StatesShow Abstract
Stability and availability of efficient catalysts at the cathode of proton exchange membrane fuel cells (PEMFC)s is a critical challenge in their commercialization. Nanoalloy catalysts are an attractive solution because these materials not only reduce the amount of Pt usually required for efficient PEMFC operation but also exhibit improved stability and selectivity. Once nanoalloys composition - atomic-level structure - catalytic properties relationships are revealed and understood well nanoalloys synthesis can be steered toward more efficient operation in PEMFCs on a rational and not trial-and-fail basis. In this respect studies on changes in the atomic-level structure of nanoalloy catalysts under realistic operating environment are particularly valuable. We will report results from recent in situ high-energy synchrotron x-ray diffraction and atomic pair distribution function studies on ternary Pt-Ni-Co and binary Pt-Co and Pd-Ni alloy catalysts at the cathode of a PEMFC designed so that interference from cell&’s anode, membrane and encasing is minimized. In situ data indicate that the increased integrity of ternary nanoalloys at atomic level contributes significantly to their superior performance.
9:00 AM - YY9.12
Quantitative Determination of the Surface C/O Stoichiometry Using Sensitivity Factors from CO and CO2 Ambient Pressure XPS Gas Phase Spectra
Matthias Hartl 3 1 Muhammed Arshad 2 Andrey Shavorskiy 3 Hendrik Bluhm 3
1Julius Maximilians University of Wuerzburg Wuerzburg Germany2Lawrence Berkeley National Laboratory Berkeley United States3Lawrence Berkeley National Laboratory Berkeley United StatesShow Abstract
Ambient pressure X-ray photoelectron spectroscopy (APXPS) is a valuable tool for the investigation of surfaces under operating conditions. Most experiments require the quantitative determination of the chemical composition of the sample, often as a function of probing depth, which can be varied in synchrotron-based APXPS by changing the incident photon energy and thus the electron kinetic energy. To determine the precise elemental composition over a wide range of kinetic energies it is essential to use experimentally measured sensitivity factors for the core levels of interest. Recently it has been reported that intramolecular inelastic scattering processes can lead to deviations from the expected relative intensities of core level peaks.  A common method for the determination of C1s-to-O1s sensitivity factors in APXPS is the measurement of gas phase CO or CO2 spectra, where the sensitivities can in principle be determined from the known stoichiometry of the molecule and the measured C1s and O1s peak areas. Here we present relative C/O sensitivity factors determined from CO and CO2 gas phase spectra over the kinetic energy range from 30 eV to 800 eV and discuss their validity for determining the C/O stoichiometry at surfaces.
 J. Söderström et al., Nonstoichiometric Intensities in Core Photoelectron Spectroscopy, Physical Review Letters 108, 193005 (2012).
9:00 AM - YY9.13
In-Situ Characterization of Ferromagnetic Thin Films
Davil Garcia 1 Sandeep Kumar 1
1UC, Riverside Riverside United StatesShow Abstract
Control of magnetic properties in ferromagnetic materials has been an overarching goal for potential applications in magnetic storage and spintronics devices. In this work we report reversible reduction in coercivity of Co/Pd multilayer thin films under high density DC biasing. We carried out in-situ focused MOKE measurement while the specimen is under DC bias. These experiments show a reduction in coercivity during the application of direct current. We propose this reduction is results from the electromigration induced stresses and resulting grain rotation.
9:00 AM - YY9.14
In-Situ Structural Determination of Monometallic and Bimetallic Nanoparticles during Electrocatalysis Using High-Energy X-Ray Diffraction, Pair Distribution Function Analysis, and X-Ray Absorption Spectroscopy
Nicholas Bedford 1 Lauren F Greenlee 2 Andrew Herring 3
1National Institute of Standards and Technology Boulder United States2National Institute of Standards amp; Technology Boulder United States3Colorado School of Mines Golden United StatesShow Abstract
Electrocatalytic chemical conversion reactions are an attractive source of alternative energy when used in fuel cell or electrolysis applications. While substantial progress has been made over decades of research, wide-spread utility of electrocatalytic power conversion or chemical synthesis is still limited on a commercial scale. A lack of understanding fundamental structure/function relationships, particularly during catalytic events, is a significant hurdle limiting rational catalyst development and commercialization. In this work, high-energy X-ray diffraction (HE-XRD) coupled with atomic pair distribution function (PDF) analysis along with X-ray absorption spectroscopy (XAS) are performed during electrocatalytic methanol oxidation to determine voltage dependences on local chemistry and structural order. EXAFS provides critical element-specific chemical and structural information within the first coordination sphere, which PDF analysis provides additional structural details over a larger size scale (~ 4 nm). Performing these experiments during electrocatalytic methanol oxidation yields structural insights that are used to assess catalytic properties that are lacking from ex-situ experimentation. Examples will include monometallic Pt and Pd nanoparticles, along with bimetallic PdAu and FeNi catalytic systems.
9:00 AM - YY9.16
In Situ X-Ray Absorption Spectroscopy Characterization of the Incipient Growth of ZnO Thin Films by Atomic Layer Deposition
Manh Hung Chu 1 Liang Tian 2 Ahmad Chaker 2 Valentina Cantelli 2 Raphael Boichot 3 Alexandre Crisci 3 Hubert Renevier 2 Toufik Ouled 4 Marie-Ingrid Richard 4 Dillon Fong 5 Dominique De Barros 2 Jean Luc Deschanvres 2 Gianluca Ciatto 1
1Synchrotron SOLEIL L'Orme des Merisiers, Saint-Aubin, Gif-sur-Yvette France2Laboratoire des Mateacute;riaux et du Geacute;nie Physique, Grenoble INP-MINATEC 3 parvis L. Neacute;el, Grenoble France3SIMap CNRS, Grenoble INP, UJF Saint Martin D'Hegrave;res France4Aix Marseille Universiteacute;, CNRS, IM2NP UMR 7334 Marseille France5Argonne National Laboratory Argonne United StatesShow Abstract
Zinc oxide semiconductors have received great attention because of their desirable properties such as a wide band gap of 3.37 eV, high exciton binding energy at room temperature, good conductivity and high transparency in the visible region . These features make ZnO thin films highly suitable for room temperature ultraviolet optoelectronic devices and transparent conductive electrodes in solar cells. Deposition of such thin films by the atomic layer deposition (ALD) method  has attracted increasing interest due to the ability to produce conformal material layers with thickness in the nanometer range. Deposition on Si substrates is particularly interesting for integration with standard microelectronics. However, despite the many successes of ZnO growth by ALD, the growth mechanism in the early stages is still not sufficiently understood. So far, by means of in situ synchrotron X-ray scattering and fluorescence, Fong et al. suggested that ZnO films grow as islands on Si substrate at the initial stage . However, the nucleation process and detailed structure of the ZnO films during the first ALD cycles has not been addressed yet.
In this work, by using in situ X-ray absorption spectroscopy in combination with ab initio simulations of the near Zn K-edge absorption cross section (XANES), we address the detailed local structure of the incipient growth of ZnO thin films during the very first ALD cycles. Zn K-edge XANES were simulated using a full-potential finite differences approach. A good agreement between the simulated Zn K-edge XANES spectrum for bulk wurtzite ZnO and the experimental spectra starting from the second ALD cycle indicates that ZnO films with the expected wurtzite type structure and high structural order are formed very soon in the growth process. In contrast, the Zn K-edge XANES spectrum of the ZnO film acquired at the end of the first cycle is considerably different. Very good agreement was found between this experimental spectrum and a XANES calculation performed using a model with O atoms in the first atomic shell around Zn, and a second shell containing Si atoms, in a local symmetry similar to the one of the hemimorphite structure. Preliminary thermodynamic calculations suggest that hemimorphite is a stable form under the experimental conditions (pressure, temperature, etc.) of the first cycle.
This present work is, to the best of our knowledge, the first X-ray absorption investigation ever performed during ZnO thin films growth and the overall findings provide a deeper understanding of the initial nucleation stages of ZnO and bonding to the Si substrate during the ALD process.
S. J. Pearton et al. Prog. in Mater. Science 50, 293 (2005).
T. Tynell et al.Semicond. Sci. Technol. 29, 043001 (2014).
D. D. Fong et al.Appl. Phys. Lett.97, 191904 (2010).
9:00 AM - YY9.17
Controlling Platinum Silicide Formation - An In Situ TEM and XPS Investigation of a Novel Material for Energy Applications
Frank Streller 1 Rahul Agarwal 1 Filippo Mangolini 1 Robert W. Carpick 2
1University of Pennsylvania Philadelphia United States2University of Pennsylvania Philadelphia United StatesShow Abstract
The extreme conditions found in many energy-related applications often demand the development of new compositions and phases of materials, and the assessment of their kinetic behavior. One way to precisely tune the crystal structure and stoichiometry of thin films is through solid-state diffusion. This method is relatively unexplored, yet intriguing for tuning film properties and in understanding the thermal behavior of solids exposed to extreme conditions. Metal silicides (MexSi) are a particularly interesting class of materials which can be formed through solid-state diffusion. They are widely used industrially, including in many energy applications, due to their rare combination of thermal stability, mechanical robustness, and metallic electrical properties. Applications of MexSi include Ohmic contacts, gate electrodes, local interconnects, and in thermoelectric devices. Despite this, the lack of fundamental understanding of the relevant solid-state diffusion processes limits the ability to tune the crystal structure, stoichiometry, and the resulting properties for MexSi thin films.
Here, we explore both source-limited and kinetically-limited solid-state diffusion as two routes to tune the stoichiometry of platinum silicide (PtxSi) thin films #8210; a popular MexSi that is of specific interest for applications under extreme conditions, including as nanoelectrical contacts for energy-efficient computing. Source-limited solid-state diffusion uses the precise control of the precursor thin film layer thicknesses, which predetermine the achievable silicide stoichiometry after annealing. Kinetically-limited solid-state diffusion utilizes a precisely controlled time-temperature regime to obtain the desired silicide stoichiometry and phase. We sputter-coated silicon nitride transmission electron microscope (TEM) support grids with thin layers of amorphous silicon (a-Si) and platinum (Pt). Using in situ heating experiments inside a TEM while performing real-time electron diffraction we showed that both diffusion routes lead to stoichiometrically-controlled formation of PtxSi (x = 1, 2, 3) thin films with high phase selectivity. We determined the crystal structure and formation sequence for all three phases. Subsequent ex situ and in situ X-ray photoelectron spectroscopy (XPS) analysis determined the film stoichiometry and confirmed the phase selectivity.
The results demonstrate, for the first time, that: (1) the diffusion processes during PtxSi-formation using sequentially-deposited layers of Pt and a-Si significantly differs from the well-studied Pt/single-crystal silicon system; and (2) the formation of Pt3Si. This Pt-rich phase has not been reported elsewhere and is especially attractive for applications. Overall these results highlight the opportunity that a precise control of the solid-state diffusion process presents in accessing novel applications fields by tailoring the stoichiometry and crystal structure of thin films.
9:00 AM - YY9.18
Imaging Corrosion Behavior of Pt Nanoparticles Using a Liquid Flow Cell in TEM
Jianbo Wu 1 Wenpei Gao 1 Hong Yang 2 Jian-Min Zuo 1
1University of Illinois at Urbana-Champaign Urbana United States2University of Illinois Urbana United StatesShow Abstract
Imaging in liquid at the enhanced resolution with nanoscale or atomic levels inside a transmission electron microscope (TEM) shows great promise for the real time study of liquid phase reactions. A capsulated liquid cell is usually composed of ultra-thin Si3N4 windows and holds a <500 nm thick liquid layer in between.1,2 In a regular liquid cell, all the reactants are pre-mixed in the cell and the reaction can be observed only after introducing the cell into TEM. It limits the type of reactions that can be studied. The reaction cannot be too fast or too slow for two major reasons: 1) the rapid reaction might occurs outside during assembling a liquid cell, which takes significant amount of time to complete, and 2) to observe the entire slow reaction, long exposure time is required. It turns out that electron beam irradiation can largely alter solution chemistry due to various effects such as heating, charging and production of free radicals.3
In this talk, we report an observation of the corrosion behavior on Pt nanoparticles. The experiment is enabled using a fluid liquid cell designed by Hummingbird Scientific. This setup enables the study of rapid reaction by pumping the reactants into the liquid cell after the introduction of the cell into TEM. Then the initiation of the reaction can be observed during TEM observation. Various shapes of Pt nanoparticles, which were previous reported,4-6 are chosen to study the etching behaviors of Pt nanoparticles during the corrosion process. With the high time resolution under TEM observation, the kinetics of Pt surface etching could be studied.
1. M. J. Williamson, R. M. Tromp, P. M. Vereecken, R. Hull, F. M. Ross, Nature Materials 2 532 (2003)
2. H. Zheng, R. K. Smith, Y. W. Jun, C. Kisielowski, U. Dahmen, P. A. Alivisatos, Science 324, 1309 (2009)
3. J. M. Grogan, N. M. Schneider, F. M. Ross, H. H. Bau, Nano Lett. 14, 359 (2014)
4. W. Zhou, J. B. Wu, H. Yang, Nano Lett. 13, 2870 (2013)
5. J. B. Wu, L. Qi, H. J. You, A. Gross, J. Li, H. Yang, J. Am. Chem. Soc., 134, 11880 (2012)
6. J. B. Wu, A. Gross, H. Yang, Nano Lett., 11, 798 (2011)
9:00 AM - YY9.19
Thermal Shock Induced Phases Transformation and Microstructural Changes in a Novel Hydrogen Transport Membrane
Lily, Yongjun Zhang 1 Sukumar Bandopadhyay 1 Uthamalingam Balachandran (Balu) 2 Nagendra Nag 3
1University of Alaska Fairbanks Fairbanks United States2Argonne National Lab Lemont United States3Surmet Corp. Burlington United StatesShow Abstract
Most research conducted in hydrogen transport membranes (HTMs) is currently focused in the areas of separation technologies and characterizations of hydrogen fluxes. No significant work has been performed on thermo-mechanical properties of HTMs at elevated temperatures and/or under various chemical environments. The effect of thermal cycles or thermal shock on the mechanical properties and the stability of the membranes are also very critical. This paper will present the thermal shock behaviors of a novel hydrogen transport membrane (HTM) cermet. In order to study the effects of the thermal shocks, the samples were soaked in air in a customized thermal cycling rig in the temperature range between 50-850°C. Scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) was used to visualize the microstructural morphology changes in the magnification up to 10000X and analyze chemical composition of the specimen by X-ray spectrum acquisition and X-ray mapping. Elemental composition analysis and semi-quantitative analysis of the HTM after 120 and 500 thermal cycles were performed by the techniques of X-ray florescence (XRF) and the electron microprobe that is equipped with EDAX energy dispersive spectrometers (EDS). Both SEM and Microprobe analysis show that the temperature gradient during thermal cycling produced more micro-cracks inside the HTM Disc, whereas the chemical reaction between Pd and Oxygen to form PdO disturbed the continuity of Pd-YSZ dual interconnection system from surface down. As the treatment of thermal cycling increased from 0 to 500 cycles, the mass fraction of Pd is greatly reduced from 74% to 12%, whereas, increased amount of PdO is produced by the oxidation of Pd with O2. The other zirconia phases, including both M-ZrO2 and YSZ, did not change significantly with the treatment of up to 500 thermal cycling between 50 to 850°C.
9:00 AM - YY9.20
Synthesis of CdS Nanocrystals in Polymeric Films Studied by In-Situ GID and GISAXS
Tiziana Di Luccio 1 Dina Carbone 2 3 Silvia Masala 4
1ENEA Portici (Naples) Italy2MAX IV Laboratory Lund University Lund Sweden3European Synchrotron Radiation Facility ESRF Grenoble France4King Abdullah University of Science and Technology (KAUST) Thuwal Saudi ArabiaShow Abstract
The synergy among different disciplines in the field of nanotechnology is giving much impulse to hybrid organic/inorganic nanocomposites to tailor functional properties. A class of hybrid nanocomposites can be obtained by combining polymeric materials and inorganic nanocrystals for their peculiar electronic, optical and catalytic properties due to quantum-size effects.
Our interest towards nanocrystal/polymer nanocomposites is motivated by their application in hybrid devices. In particular,we have synthesized II-VI semiconducting nanocrystals (NCs) within a polymer matrix thus avoiding ex-situ blending procedures that may have agglomeration and phase segregation as main drawbacks. The synthesis process of the NCs (here camdium sulfide, CdS) involves the addition of a metal precursor to a polymer in solution and spin coating of the blend. A thermal treatment of the deposited film causes the decomposition of the precursor and the CdS NCs growth within the polymer. In bulk films obtained by drop casting we found that the nanoparticle size and aggregation depend upon the annealing conditions, namely temperature and duration of the treatment. Morevoer, the same process works with both amorphous insulating polymers as polystyrene and topas and semicrystalline conjugated polymers such as P3HT employed in hybrid solar cells. We believe that the device performance can be greatly improved if the growth and dispersion of the NCs within the polymer matrix are carefully controlled since the very first stages of their formation.
In this work we describe both ex-situ and in-situ experiments of grazing incidence diffraction (GID) and grazing incidence small angle scattering (GISAXS) under different annealing conditions on thin films (20-30 nm) performed at beamline ID01 at ESRF. While during the ex-situ experiments the crystalline signal from the NCs was weak and hardly detectable, the in-situ studies gave very different results. 2D GISAXS images showed that the precursor crystal structure changed by effect of the temperature above 100°C. At 150°C new diffraction peaks arranged in hexagonal symmetry were observed, corresponding to a distance of about 2.7 nm. This peculiar diffraction pattern became very well defined at 170°C. Correspondingly, at 170°C GID scans showed strong crystalline peaks from cubic CdS NCs of about 2 nm size. With increasing temperature, these peaks become more intense and sharper. These results indicate that at 170°C the QDs are close packed and regularly arranged in an hexagonal 3D lattice with lattice parameter of 2.7nm. Such ordered state disappears for annealing above 220°C. The main results is that a temperature of 170°C is sufficient to synthesize the CdS NCs in thin polymeric films, while in the bulk system a higher temperature by at least 30°C is needed. Reducing the annealing temperature prevents the degradation of the polymer matrix and represents an important issue for the device realization and performances.
9:00 AM - YY9.21
In-Situ Characterization of Ni/NiO Core/Shell Structure Photo-Corrosions on TiO2 for Water Splitting
Liuxian Zhang 1 Peter A. Crozier 1 Qianlang Liu 1 Toshihiro Aoki 1
1Arizona State University Tempe United StatesShow Abstract
Photocatalysts have potential applications for solar fuel generation either through water splitting or CO2 reduction. The Ni/NiO core/shell structure is one of the most efficient co-catalysts for solar water splitting when coupled with suitable semiconducting oxides. However, Ni/NiO core/shell structures on TiO2 are only able to generate H2 but not O2 in aqueous water. It is now recognized that atomic level in situ observations are critical for understanding the structure-reactivity in photocatalysts in the presence of reactant and product species and during in-situ light illumination. Herein we use TiO2 as a model material to develop in situ photocatalytic experimental methodology and explore structure changes of Ni/NiO core/shell on oxide semiconductor photocatalysts. Here we employ a modified ETEM with a broadband light source to study the nature of the hydrogen evolution reaction in these systems correlating photochemical H2 production with atomic resolution structure.1 During the H2 evolution reaction, the metal core initially formed partial voids which grew and eventually all the Ni diffused out of the core-shell into solution leaving an inactive hollow NiO void structure. This photocorrosion occurred either due to direct contact with the water through cracks or a Kirkendall effect where Ni diffused along grain boundaries in the NiO shell onto the particle surface where dissolution took place. This observation is also achieved ex-situ when exposed to gas phase water vapor. In situ characterization is utilized to explore the possible p