Artur Braun Empa – Swiss Federal Laboratories for Materials Testing and Research
Jinghua Guo Lawrence Berkeley National Laboratory
Randall E. Winans Argonne National Laboratory
Helmut Schober Institut Max von Laue - Paul Langevin (ILL)
W1: Solid Oxide Fuel Cells and Electronic Structure of Ceramics
Tuesday PM, April 06, 2010
Room 3004 (Moscone West)
9:45 AM - W1.1
Chemistry, Structure and Transport Processes in Solid Oxide Fuel Cell Components Investigated With X-ray and Neutron Methods.
Artur Braun 1 , Selma Erat 1 , Peter Holtappels 1 , Thomas Graule 1 2 , Markus Janousch 3 , Josef Sfeir 7 , Jan Ilavsky 10 , Andrew Allen 9 , Robert Steinberger-Wilckens 6 , Jan Embs 5 , Thierry Straessle 5 , Eberhard Lehmann 4 , Jari Kiviaho 8 , Zhi Liu 11 Show Abstract
1 Laboratory for High Performance Ceramics, EMPA, Dübendorf Switzerland, 2 , TU Bergakademie Freiberg, Freiberg Germany, 3 Swiss Light Source, Paul Scherrer Institut, Villigen Switzerland, 7 , Hexis AG, Winterthur Switzerland, 10 Advanced Photon source, Argonne National Laboratory, Argonne, Illinois, United States, 9 , US NIST, Gaithersburg, Maryland, United States, 6 , Forschungszentrum Jülich, Jülich Germany, 5 Laboratory for Neutron Scattering, Paul Scherrer Institut, Villigen Switzerland, 4 SINQ, Paul Scherrer Institut, Villigen Switzerland, 8 , VTT, Espoo Finland, 11 Advanced Light source, Lawrence Berkeley National Laboratory, Berkeley, California, United States
The all-ceramic solid oxide fuel cell is a good example to illustrate the complexity of electrochemical energy conversion devices.A detailed overview is presented about how either component can be subject to in-depth studies with respect to structural properties, chemistry, and functionality.For the anode - the fuel electrode - it is shown how sulfur poisoning and sulfur-anode interaction can be addressed with element specific x-ray absorption spectroscopy. Here in particular S(1s) x-ray absorption near-edge spectra show some unexpected chemistry going on during fuel cell operation.For the ceramic electrolytes we show the example for proton conductors, where quasi elastic neutron scattering is employed to measure the proton diffusivity and thus proton conductivity as a function of temperature. This quantity is compared with electrochemical impedance spectroscopy data.For the cathodes we show a suite of soft x-ray and photoelectron spectroscopy data correlate quantitatively with the electronic conductivity of iron perovskites as a function of temperature and A-site and B-site substitution. A Braun, M. Janousch, J. Sfeir, J. Kiviaho, M. Noponen, F. E. Huggins, M. J. Smith, R. Steinberger-Wilckens, P. Holtappels, T. Graule, Molecular speciation of sulfur in solid oxide fuel cell anodes with x-ray absorption spectroscopy, J. Power Sources 2008,183, 2, 564-570.  J. Richter, A. Braun, A.S. Harvey, P. Holtappels, T. Graule, L.J. Gauckler, Valence changes of manganese and praseodymium in Pr(1–x)Sr(x)Mn(1–y)In(y)O(3–δ) perovskites upon cation substitution as determined with XANES and ELNES. Physica B 2008, 403(1) 87-94.  A Braun, S. Duval, J.P. Embs, F. Juranyi, P. Ried, P. Holtappels, R. Hempelmann, U. Stimming, Th. Graule. Proton diffusivity in the BaZr0.9Y0.1O3-delta proton conductor. Journal of Applied Electrochemistry, 2009, 39(4), 471-475. O. Haas, U.F. Vogt, C. Soltmann, A. Braun, W.-S. Yoon, X.Q. Yang, T. Graule. The Fe K-edge X-Ray Absorption Characteristics of La1-xSrxFeO3-δ Prepared by Solid State Reaction. Materials Research Bulletin 44 (2009), pp. 1397-1404. A.J. Allen, J. Ilavsky, A. Braun, Multi-Scale Microstructure Characterization of Solid Oxide Fuel Cell Assemblies with Ultra Small-Angle X-Ray Scattering, Advanced Engineering Materials 2009, 11 (6), 495-501. A Braun, X. Zhang, Y. Sun, U. Müller, Z. Liu, S. Erat, M. Ari, H. Grimmer, S.S. Mao, T. Graule, Correlation of high temperature X-ray photoemission valence band spectra and conductivity in strained LaSrFeNi-oxide on SrTiO3(110), Applied Physics Letters, 95, 022107, 2009.
10:00 AM - W1.2
In-situ Studies of Changes in Phonon Spectra Across the Ferroelectric to Paraelectric Phase Transitions in Model Ferroelectrics.
Narayani Choudhury 1 5 , Alexander Kolesnikov 2 , Helmut Schober 3 , Eric Walter 4 , Mark Johnson 3 , Doug Abernathy 2 , M. Lucas 2 Show Abstract
1 Dept. of Physics, University of Arkansas, Fayetteville, Arkansas, United States, 5 Solid State Physics Division, Bhabha Atomic Research centre, Mumbai India, 2 Neutron Scattering Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 3 , Institut Laue-Langevin, Grenoble, Cedex, France, 4 , College of William and Mary, Williamsburg, Virginia, United States
Ferroelectric materials interconvert electrical and mechanical energies and find key technological applications as piezoelectric transducers and actuators used in ultrasonic devices, medical imaging, and telecommunications. The functional behavior of these materials, including its dielectric, piezoelectric and elastic response is intimately connected to their phonon spectra and lattice dynamics. Detailed ab initio lattice dynamics studies and inelastic neutron scattering (INS) measurements of model perovskite ferroelectrics  revealed that distinct bonding characteristics in the ferroelectric (FE) and paraelectric (PE) phases give rise to spectacular vibrational signatures. These studies  have also illustrated the important role of vibrational spectroscopy in novel materials design. Here we report, INS measurements and ab initio lattice dynamics calculations for studies of the in-situ changes in vibrational spectra across the FE-FE and FE-PE phase transitions in PbTiO3 and BaTiO3. There are radical changes in material behavior across the FE-PE transition and such studies are of interest to understand the microscopic correlations between vibrational spectra and functional properties. While both PbTiO3 and BaTiO3 are ferroelectric, SrTiO3 is a quantum paraelectric. The ferroelectric phase in SrTiO3 is suppressed even as T→0 K by zero-point fluctuations. Intrinsic differences in the bonding in BaTiO3, PbTiO3 and SrTiO3 give rise to their vastly different phase diagrams and FE behaviors [1,2]. These in turn give rise to interesting manifestations in their PDOS, which is the key quantity that determines various thermodynamic properties. Time-of-flight INS measurements of the PDOS as a function of temperature have been carried out using the HRMECS spectrometer at the Intense Pulsed Neutron Source, Argonne National Lab., the ARCS spectrometer at the Spallation Neutron Source, Oak Ridge National Lab. and at the Institut Laue Langevin to characterize the changes in PDOS across the FE-FE and FE-PE phase transitions of PbTiO3 and BaTiO3. Changes in phonon spectra across the antiferrodistortive transition of SrTiO3 have also been studied. The experiments have been analyzed using accurate density functional perturbation theory calculations. Theoretical lattice dynamics studies have been employed to derive the phonon and neutron weighted spectra, infrared reflectivity spectra and thermodynamic properties like the specific heat and equation of state. The observed specific heat of PbTiO3 exhibits a sharp discontinuity across the first order FE to PE phase transition; inclusion of excess entropy and latent heat terms are required to help explain this complex thermodynamic behavior. The integration of theory and experiments provides a fundamental atomic level understanding of material behavior in these systems. N. Choudhury et al., Phys. Rev. B 77, 134111 (2008).  R.E. Cohen, Nature 358, 156 (1992).
10:15 AM - W1.3
Dynamics of Nanocage-based Materials Revealed by Neutron Scattering Experiments and First Principle Powder Averaged Lattice Dynamics Calculations.
Michael Koza 1 2 , Andreas Leithe-Jasper 2 , Yuri Grin 2 , Hannu Mutka 1 , Romain Viennois 3 , Zenji Hiroi 4 , Peter Franz 6 , Didier Ravot 3 , Mark Johnson 1 , Martin Rotter 5 Show Abstract
1 , Institut Laue Langevin, Grenoble France, 2 CPfS, Max Planck Institut, Dresden Germany, 3 LPMC, Univeriste de Montpellier II, Montpellier France, 4 ISSP, University of Tokyo, Tokyo Japan, 6 , University of Vienna, Vienna Austria, 5 Physics Department, University of Oxford, Oxford United Kingdom
The direct conversion of waste heat into electrical power in thermoelectric devices is believed to contribute substentially to future power supply and sustainable energy management. Nanocage-based crystalline structures like filled skutterudite systems XFe4Sb12 (X = Ca, Cs, Ba, La, Ce, Yb, Nd, ...) and clathrate materials like BaGe and BaSi have attracted some scientific interest as they are sought to be excellent thermoelectric materials. Their applicability for an efficient conversion of thermal into electrical energy is based on the opportunity of tuning appreciably the heat transport through the sample leaving the electron transport rather uneffected. For example, by a progressive filling of the voids in a Co4Sb12 skutterudite with guest atoms, e.g., La or Ce, the thermal conductivity drops by two orders of magnitude when the filling ratio is about 50 % . Since glasses display a reduced thermal conductivity as compared with their crystalline counterparts it has been deduced that the mechanisms in nanocage structures and glasses might be the same, furthermore controlled by the specific phonon modes associated with the guest atoms, believed to be independent rattling modes in the cages of the host structure. The introduced nanocage-based materials are therefore termed 'electron crystals and phonon glasses'.A comprehensive description of the basic physical principles underlying the low thermal conductivity is required to enable an ad hoc design of thermoelectric devices. Our approach towards the understanding of this effect is based on neutron scattering experiments assisted by different computer simulation and calculation tools, like ab initio lattice dynamics. Neutron scattering is a powerful experimental technique since the kinematic properties of the neutron probe matches perfectly the energy and momentum scales of phonons, i.e., the very carriers of heat energy. Characteristic finger prints of the guest-dynamics in filled nanocage structures can be studied in detail.We will give some examples of our work on filled skutterudite and clathrate structures and pyrochlore osmates XOs2O6 (X = K, Rb, Cs) [3,4]. From an academic point of view, pyrochlore osmates seem to be excellent candidates for unravelling the mystery of ‘rattling’ dynamics in nanocage structures. We will present a new approach based on ab initio lattice dynamics calculations towards the interpretation of experimental data particularly dedicated to polycrystalline systems. G.P. Meisner, D.T. Morelli, S. Hu, J. Yang, and C. Uher, Phys. Rev. Lett. 80, 3551, (1998). B.C. Sales, D. Mandrus, B.C. Chakoumakos, V. Keppens, and J.R. Thompson, Phys. Rev. B. 56, 15081, (1997). M.M. Koza, M.R. Johnson, R. Viennois, H. Mutka, L. Girard and D. Ravot, Nature Materials 7, 805, (2008) H. Mutka, M.M. Koza, M.R. Johnson, Z. Hiroi, J.-I. Yamaura and Y. Nagao, Phys. Rev. B 78, 104307, (2008)
10:30 AM - **W1.4
Energy Research at Paul Scherrer Institute’s Large-scale Facilities.
Joel Mesot 1 Show Abstract
1 , Paul Scherrer Institute, Villigen Switzerland
Beside running three large scale facilities (muon, neutron, synchtrotron) one of the main research focus at the Paul Scherrer Institute (PSI) is on energy sciences. In order to make best use of this unique constellation at PSI, dedicated beamlines (BL) have been developed in the past 10 years to investigate problems related to energy and environmental issues. In this talk I shall review the latest developments obtained at the Neutron- and x-ray micro radiography BL (fuel cells); in situ XAS BL (catalysts), VUV-spectroscopy BL (chemical reactions) and in-situ diffraction studies (micro- and nano-size materials).
11:00 AM - W1: SOFC I
11:30 AM - W1.5
Performance Improvement of Solid Oxide Fuel Cell Using Platinum Modification.
Xubin Pan 1 , Iliana Medina-Ramirez 2 , Jinbo Liu 3 Show Abstract
1 Environmental Engineering, Texas A&M University - Kingsville, Kingsville, Texas, United States, 2 Chemistry, Universidad Autonoma de Aguascalientes, Aguascalientes Mexico, 3 Chemistry, Texas A & M University – Kingsville, Kingsville, Texas, United States
Fuel cells are green energy sources that spontaneously convert chemical energy into electricity, releasing heat and water when reduction oxidation reactions occur. One class called solid oxide fuel cells (SOFC) are devices drawing significant attention. Studies on SOFC cathode materials are critical to improve the performance of SOFC device due to its complexity of reducing oxygen. The lanthanum strontium cobalt iron oxide (LaxSr1-xCoyFe1-yO3, LSCF) displays high catalytic activity for O2 reduction reaction (ORR), high ionic and electronic conductivity at an intermediate temperature. Platinum modification on LSCF induces its band gap energy decrease, which allows rapid electron transfer from valance to conduction band, consequently ORR is advanced. In this study, CeO2 based materials were used as the electrolyte because LSCF cathode shows poor compatibility with traditionally used yttria stabilized zirconia (YZS).Sol-Gel method followed by Pt modification was used to improve fuel cell performance and to achieve high specific surface area of LSCF and Pt-LSCF. The kinetics of SOFC was evaluated using redox rate (exchange current density, io). The DC polarization was conducted to identify io when overpotentials (η) of -0.7 - +0.7 V were applied and temperatures varied from 400 to 700 °C with an interval of 50 °C. 3-electrode cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were implemented. EIS was performed to establish resistance-free i/η relationship, when the frequency varies from 0.05-106 Hz. Comparison indicates the Pt modification significantly improves io at identical operating conditions. It can be seen the specific area resistance from EIS and io were reached at ca. 0.30 Ω×cm2 and 250 mA/cm2 for LSCF and 0.12 Ω×cm2 and 565 mA/cm2 for Pt-LSCF at 700°C, respectively. Nanostructural characterization was implemented using high resolution transmission/scanning electron microscopy (HRTEM/SEM), X-ray powder diffraction (XRD) and wavelength dispersive spectroscopy (WDS). TEM/SEM images depict that the diameter of cathode materials is approximately 20-50 nm to enlarge its surface area (5.6 m2/g), which allows the rapid gas diffusion and instantaneous chemisorption of O2. TEM morphology showed that highly crystalline and mono-dispersive LSCF and Pt-LSCF nanoparticles. XRD results indicate that the nanoparticles are well aligned with standard LSCF perovsike and Pt cubic. Crystallite size obtained from Scherer equation corresponds with the TEM/SEM measured size. Elemental mapping from WDS shows that all elements (La, Sr, Co, Fe and Pt) distribute uniformly.
11:45 AM - W1.6
Electronic and Crystallographic Structure of LaSrFeNi-oxides: Potential Cathode Materials for Solid Oxide Fuel Cells.
Selma Erat 1 2 , Artur Braun 1 , Alejandro Ovalle 1 , Cinthia Piamonteze 3 , Zhi Liu 4 , Ludwig Gauckler 2 , Thomas Graule 1 5 Show Abstract
1 , Empa, - Swiss Federal Laboratories for Materials Testing & Research, Dubendorf Switzerland, 2 Department for Nonmetallic Inorganic Materials, ETH-Zurich, Zurich Switzerland, 3 Swiss Light Source, Paul Scherrer Institute, Villigen Switzerland, 4 Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 5 , Technische Universität Freiberg, Freiberg Germany
Solid oxide fuel cells (SOFCs) are electrochemical devices which produce electricity directly from oxidizing a fuel. SOFCs have three main parts; anode, cathode and electrolyte. We work on LaSrFeNi-oxides as a potential cathode material for intermediate temperature SOFCs. The electrical conductivity of LSF-Ni oxides which show semiconducting behavior at elevated temperatures and metallic like behavior at high temperatures explained in terms of changes in crystallographic structure monitored by temperature dependent neutron diffraction, in microstructure and in electronic structure, as well. In order to investigate the electronic structure, we used X-ray absorption spectroscopy technique and supported with the theoretical calculation depending on Ligand Field Atomic Multiplet Theory. We get very good agreement between experimental results and theoretically calculated results. For example, La0.5Sr0.5Fe0.75Ni0.25O3 which has higher conductivity has 50% Fe3+ and 50% Fe4+, both in high spin state with 10Dq=1.85 eV. In addition to that, the hybridization between Fe/Ni 3d and O 2p orbitals is stronger than La1-xSrxFe-oxides which make the Ni containing samples more conducting. The transport properties of the Ni containing samples can be explained by two different mechanisms: electron hole hopping via superexchange unit Fe3+-O-Fe4+ and charge transfer from O 2p to Ni 3d.
12:00 PM - **W1.7
Strong Correlation in Transport Properties Between Holes/Protons and B-site Multivalent Cations in Perovskite Oxides for SOFC Materials by XAS and RPES/RIXS.
Take0 Kikuchi 1 , Mao Tamaru 1 , Tohru Higuchi 2 , Jinghua Guo 3 , Shu Yamaguchi 1 Show Abstract
1 Dept. of Materials Science, University of Tokyo, Tokyo Japan, 2 Dept. of Appl. Phys., Tokyo University of Science, Tokyo Japan, 3 ALS, Laurence Berkeley National Lab., Berkeley, California, United States
A strong correlation in electrical transport properties between holes/protons and B-site multivalent cation in perovskite oxides were found in acceptor- and donor-doped BaPrO3 and BaZr1-xPrxO3 systems. In case of BaPrO3, auto-ionization which corresponds to the electron transfer from O2- to Pr4+ to form O-(hole) and Pr3+(electrons) pairs, is favored. Such strongly correlated electron-hole pair is observed by soft X-ray absorption spectroscopy (XAS) and Raman inelastic X-ray scattering (RIXS) measurements and the charge transfer from Pr4f0-O2p6 to Pr4f1-O2p5 is identified. The electrical transport properties are examined by both the electrical conductivity and thermoelectric power measurements, showing a possible small polaron hopping for both electrons and holes with similar estimated mobility of 10-3~10-4 cm2V-1s-1. Due to a strong correlation with the interaction energy of ≈2.2 eV, a strange correlated migration of holes and electrons that cannot carry net charge is estimated. Recent report on a careful examination of partial electronic conductivity for CeO2 systems exhibits similar situation of strongly correlated carrier formation by the auto-ionization. A possible extension of auto-ionization and relating electronic band structure for proton/electrons on transition metal cation will be discussed.
W2: Solid Oxide Fuel Cells and Solid State Ionics
Tuesday PM, April 06, 2010
Room 3004 (Moscone West)
2:30 PM - W2.1
Dynamic Instability at the Origin of Oxygen Ion Conduction in Solid Oxides at Ambient Temperature.
Helmut Schober 1 , Werner Paulus 2 , Mark Johnson 1 , Stefan Eibl 2 , Monica Ceretti 2 , Carlo Lamberti 3 , Marie Plazanet 1 , Ollivier Hernandez 2 Show Abstract
1 Science Division, Institut Laue Langevin, Grenoble France, 2 Sciences Chimiques de Rennes, CNRS-Universite de Rennes1, Rennes France, 3 , University of Turin, Turin Italy
The conduction of ions in solids is of paramount importance for many technological devices like solid oxide fuel cells. It is inherent to solids that ions are trapped within potential wells. Their transport thus has to be activated at the price of elevated temperatures, a condition that is often incompatible with technological requirements. While atomic vibrations have the potential of assisting the diffusion process little is known about the exact conditions that have to be reunited to trigger such a process. Here we show that dynamic instability is responsible for the large ion conduction in SrFeO2.5 with Brownmillerite-type structure. Using ab-initio molecular dynamics calculations we observe the migration of oxygen ions away from the original lattice positions into the vacancy channels of the Brownmillerite structure. The escape of the oxygen ion is rendered possible by the destabilization of a shallow potential well due to low-lying vibrational modes, the existence of which is confirmed by neutron spectroscopy. Analyzing the lattice dynamics as a function of structural parameters it is possible to identify the structural subtleties responsible for the instability. It is found that in the isostructural compound CaFeO2.5 fast oxygen ion diffusion is absent at low temperatures. The origin of this behaviour lies with the slightly different iron-oxygen distances rendering the potentials better defined and less amenable to dynamical destabilization. The here-introduced concept of dynamical instability is not restricted to the discussed class of materials but may be applied to any system that features ion conduction at low temperatures.W.Paulus, H.Schober, S.Eibl, M.Johnson,T. Berthier, O.Hernandez, M.Ceretti,M.Plazanet, K.Conder, and Carlo Lamberti, JACS (2008)
2:45 PM - **W2.2
Hard X-rays: A Tool for Mapping Energy Materials in Space and Time.
Henning Poulsen 1 , Poul Norby 1 Show Abstract
1 Risoe National Laboratory for Sustainable Energy, Technical University of Denmark, Roskilde Denmark
During the last decade our group has developed of a number of methods for comprehensive 4D (space and time-resolved) studies at the micron scale using x-rays in the 35-200 keV. These include - 3DXRD microscopy: enabling studies of the dynamics (orientation, morphology) of several hundred of grains simultaneosusly- plastic strain tomography: mapping the deformation field- stress mapping: in crystalline as well as amorphous materials- fast time-resolved diffractionThese status of these methods will be presented and initiatives towards generalising the concepts to the nano-scale presented.The prospect of using the hard x-rays for in situ studies of materials for energy technology is illustrated with case stories from a set of applications: - studies of strain and oxidation kinetics in fuel cells and oxygen permeable membranes- studies of grain dynamics in superconducting tapes- studies of polymer composites for wind turbines
3:15 PM - W2.3
Correlation of Structure and Conductivity of Proton Conducting Ceramics.
Qianli Chen 1 2 , A. Braun 1 , A. Ovalle 1 , A. Cervellino 3 , J. Embs 3 4 , T. Straessle 3 , W. Stolte 5 , O. Safonova 6 , S. Duval 1 , W. Haeussler 7 8 , P. Holtappels 1 , V. Pomjakushin 3 , N. Bagdassarov 9 , T. Graule 1 10 Show Abstract
1 Laboratory for High Performance Ceramics, EMPA - Swiss Federal Laboratories for Materials Testing and Research, Duebendorf Switzerland, 2 Department of Physics, ETH Zurich, Zurich Switzerland, 3 Laboratory for Neutron Scattering, ETH Zurich & Paul Scherrer Institut, Villigen Switzerland, 4 , Saarland University, Saarbruecken Germany, 5 , Advanced Light Source, Berkeley, California, United States, 6 Swiss Norwegian Beamlines, ESRF, Grenoble France, 7 Physics Department, TU Munich, Garching Germany, 8 , FRM-II, Garching Germany, 9 Institute of Geoscience, University of Frankfurt, Frankfurt Germany, 10 , TU Bergakademie Freiberg, Freiberg Germany
Proton conductors are promising solid electrolyte materials for ceramic fuel cells at intermediate working temperature. Our study focuses on the molecular mechanisms of proton conductivity of peroskite yttrium doped barium zirconates and cerates, extensively with synchrotron and neutron radiation at large scale facilities. Our recent results in Y-resonant X-ray diffractograms of BaZr0.9Y0.1O2.95 (BZY10) reveal that Y atoms are organized in a superstructure. Comparison with neutron diffraction superstructure reflections in protonated/deuterated BZY10 suggests that both superstructures are linked, and that protons move in the landscape imposed by the Y. The onset temperature of lateral proton diffusion coincides with its thermal lattice expansion, which exhibits a contraction for protonated BZY10 at about T = 648 K, suggesting a correlation of toughening of the lattice and proton conductivity. The chemical shift in the Y L1-shell x-ray absorption spectra reveals a reduction from Y3+ towards Y2+ upon protonation. The Y K-edge spectra reveal a charge transfer, which vanishes at high temperatures, possibly suggesting a thermally unstable H-Y bond. We have previously found that the activation energy of proton conductivity decreases linearly with the lattice parameter, indicating that the protons need "space" to move freely in the lattice.
3:30 PM - **W2.4
Characterizing Solid Oxide Fuel Cells During Electrochemical Operation Using Ambient Pressure XPS.
Michael Grass 2 , Farid El Gabaly 1 , Anthony McDaniel 1 , Kevin McCarty 1 , Hendrik Bluhm 2 , Roger Farrow 1 , Zahid Hussain 2 , Zhi Liu 2 Show Abstract
2 Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 1 , Sandia National Laboratories, Livermore, California, United States
Electrochemical systems for energy applications are hampered by lack of fundamental measurements and understanding of ion transport and interfacial charge transfer mechanisms. Electrochemical devices based on the conduction of O2- anions through a solid electrolyte, such as a solid oxide fuel cell (SOFC) or electrolyzer (SOEC), have great potential for both clean, efficient power generation and efficient production of fuels such as hydrogen or synthesis gas. The essential physical phenomena that govern reaction and charge transfer across material interfaces are poorly understood. The ability to directly observe changes in chemical composition and elemental oxidation state at surfaces and interfaces under electrochemically active conditions will provide insight into such processes. Here, we report in situ measurements of Ni and Pt patterned thin films (300nm) electrodes in solid-oxide electrochemical cells using ambient pressure X-ray photoelectron spectroscopy (APXPS, beamlines 9.3.2 and 11.0.2 of the Advanced Light Source, Lawrence Berkeley National Laboratory). This novel setup provides quantitative information about the elemental surface composition, local surface potential of electrolyte and electrodes, and changes in elemental oxidation state as a result of electrochemical and thermochemical activity occurring under relevant operating conditions: typically 0.25 Torr of hydrogen and 0.25 Torr of water, T=1023K, and under applied bias potential. A new endstation at ALS beamline 9.3.2 allows us to map electrochemically driven surface phenomena with 20 micron resolution.
4:00 PM - W2: SOFC II
4:30 PM - **W2.5
Anomalous Ultrasmall-angle X-ray Scattering Studies of Electrochemical Interface Evolution in Solid Oxide Fuel Cells in Response to Service Life and Fuel Sulfur Content.
Andrew Allen 1 , Jan Ilavsky 2 , Pete Jemian 2 , Artur Braun 3 Show Abstract
1 Ceramics Division, NIST, Gaithersburg, Maryland, United States, 2 Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois, United States, 3 Laboratory for High Performance Materials, EMPA, Dubendorf Switzerland
The use of small-angle X-ray and neutron scattering (SAXS and SANS) methods has become widespread for quantifying nanoscale features in heterogeneous materials of all types. The primary parameters obtained are the mean size, the total surface area and, with absolute intensity calibration, the volume fraction size distribution. With the development of ultrasmall-angle scattering (USAXS and USANS) methods (that exploit crystal diffraction optics to extend the measurements to smaller scattering angles and correspondingly larger sizes), these microstructural parameters can now be determined over a contiguous length scale from nanometers to micrometers. At a 3rd generation synchrotron facility, the USAXS technique can cover much of this scale range within a single measurement, using a beam size (hence spatial resolution) down to a few micrometers in one dimension. This makes the method ideally suited to studying advanced energy materials, which frequently contain hierarchical void structures over many length scales, several co-existing solid phases, and microstructural gradients or interfaces. All of these aspects must be well characterized in order to establish the processing – microstructure – property relationships that govern performance. We have employed the USAXS technique to study a solid oxide fuel cell (SOFC) system.In the SOFC context, it is important to distinguish among the different electrochemically-active solid components and their associated void morphologies close to the electrolyte – electrode interfaces. To do this, USAXS measurements must be made at each sample position using several X-ray energies just below the X-ray absorption edge for a selected atomic species in the system. The “anomalous” variation of X-ray scattering contrast with energy can then be used to distinguish those aspects of the microstructure associated with the phase containing the selected atom. For truly multi-component systems such as SOFC’s, correlated anomalous USAXS measurements are needed at two or more widely separated absorption edges. This paper will illustrate these points through anomalous USAXS studies of a SOFC system (previously measured to obtain a basic microstructure characterization ) to obtain the electrochemically-active interface response to service life in the presence or absence of sulfur within the fuel.  A.J. Allen, J. Ilavsky and A. Braun; "Multi-scale microstructure characterization of solid oxide fuel cell assemblies with ultrasmall-angle X-ray scattering," Adv. Eng. Mater., 11, 495-501 (2009).
5:00 PM - W2.6
Neutron Diffraction Study of NiO/LiCoO2 Electrodes for Innovative Fuel Cell Development.
Roberto Coppola 1 , Paul Henry 3 , Angelo Moreno 2 , Juan Rodiguez-Carvajal 3 , Elisabetta Simonetti 2 Show Abstract
1 FISNUC, ENEA, Roma Italy, 3 , ILL, Grenoble France, 2 IDROCOMB, ENEA-Casaccia, Rome Italy
This contribution presents the results of a neutron diffraction study carried out on Ni-NiO 30% electrodes coated with LiMg 0.05 Co 0.95 O2 cobaltite deposited on the substrate by complex sol-gel process. The neutron diffraction measurements were carried out at the D20 diffractometer at the High Flux reactor of the Institut Max von Laue – Paul Langevin. The catalytic layer being only a few microns in thickness, the diffracting volume of the cobaltite phase was optimised by stacking 40 small rectangular pieces cut from the original electrode. A pure cobaltite sample was used as a reference for identifying in the complete electrode the diffraction peaks of the catalytic layer. Both an as-received sample and an electrode tested 100 h at 650 °C were measured. The adopted technique provides useful and accurate information on the crystallographic phases present the in the as-received electrode, where a cobaltite volume fraction of the order of 0.01 is estimated; after 100 h at 650°C in the cell the initial crystallographic structure is completely changed but traces of hexagonal phase are still detectable.
5:15 PM - W2.7
Total Reflection Inelastic X-ray Scattering; A Direct Probe of Defect Chemistry in Thin Films.
Tim Fister 1 , Dillon Fong 1 , Jeffrey Eastman 1 , Hakim Iddir 1 , Peter Zapol 1 , Hui Du 2 , Paul Salvador 2 , Paul Fuoss 1 Show Abstract
1 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States, 2 Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States
At the high temperatures associated with many growth techniques and thin film devices, the mobility of ionic defects can lead to strong property gradients near the surface that influence, and are influenced by, chemical and electrical boundary conditions. To study equilibrium changes in composition, valence, and electronic structure near the surface and into the bulk, we present a new approach, total reflection inelastic x-ray scattering (TRIXS). TRIXS uses highly penetrating hard x-rays (10 keV) to create an in situ alternative to traditional sub-keV spectroscopies that are generally limited to use under vacuum conditions. We demonstrate the feasibility of this new approach by characterizing a 10-nm-thick film of La0.6Sr0.4CoO3-δ (LSCO) grown epitaxially onto a (100) SrTiO3 substrate. LSCO is a prototypical mixed conductor and an important candidate material for application in intermediate-temperature solid oxide fuel cells. By comparing data acquired under total x-ray reflection and penetrating conditions, we are able to separate the oxygen K-edge spectra from a LSCO thin film from that of the underlying SrTiO3 substrate. Working at high temperature, we examine the relationship between the oxygen K-edge and the cobalt 3d final states under controlled oxygen partial pressure conditions, and make a direct measurement of the interplay between oxygen vacancy concentration and cobalt valence state. We also will describe how using a higher energy probe than comparable soft x-ray absorption measurements provides the ability to easily access dipole-forbidden final states, using the dramatic evolution of hybridized lanthanum f-electron states with momentum transfer as an example.This work is supported by the U.S. Department of Energy (DOE) Solid State Energy Conversion Alliance (SECA) program, and at Argonne by DOE under contract DE-AC02-06CH11357
5:30 PM - W2.8
3D Chemical Imaging of Solid Oxide Fuel Cells Revealed by Synchrotron X-ray Fluorescence (sub)Microtomography.
Pierre Bleuet 1 , Peter Cloetens 2 , Gerard Delette 3 , Patrice Gergaud 1 , Olivier Sicardy 3 , Remi Tucoulou 2 , Julie Villanova 3 Show Abstract
1 , CEA, LETI, MINATEC, Grenoble France, 2 , European Synchrotron Radiation Facility, Grenoble France, 3 , CEA, LITEN, Grenoble France
SOFCs are interesting power source alternatives that convert chemical energy into electrical energy at high temperatures. From the chemical point of view they are made of ceramic materials containing major and minor elements, including oxygen, nickel, zirconium, lanthanum, strontium, manganese, yttrium, cerium or gadolinium. This complex arrangement is based on a mesoscopic scale structure. To image and measure the distributions of all these elements at the very same time and in a non destructive way, we use x-ray fluorescence tomography based on a 3rd generation synchrotron source.In fluorescence tomography, a pencil, focused (or collimated) beam is produced and a sample, usually few hundred times bigger than the beam, is raster scanned along a particular axis while being rotated, so that a 1st generation of medical scanner geometry is faked. Eventually this scanning scheme can be repeated several times at several altitudes and this 3-axes motion allows 3D imaging. All along the scan, fluorescence spectra are recorded using an energy-dispersive detector placed at 90 degrees with respect to the beam. After appropriate peak fitting, so-called fluorescence sinograms can be built that serve as an input for 2D, or 3D, elemental reconstruction. Although the technique was limited to the micrometer scale until a few years back, x-ray optics progresses have recently been performed that now allows reaching 100nm resolution in the 15-30keV x-ray regime. Extension to depth-resolved crystalline imaging has also been proved, which could be of great interest for SOFCs. Experiments on SOFCs have been performed at the ESRF beamline ID22NI. Fluorescence tomography has been applied to SOFCs imaging, revealing features that cannot be observed by any other technique, including more conventional x-ray tomography or electron imaging that have also both been carried out. The principle of the method will be discussed as well as its limitations.
5:45 PM - W2.9
In-situ Electrochemical Polarization Experiments for Two-terminal Type Gapless Cu2S Atomic Switch Using Hard X-ray PES.
Takashi Tsuchiya 1 , Shogo Miyoshi 1 , Yoshiyuki Yamashita 3 , Kauya Terabe 2 , Shu Yamaguchi 1 Show Abstract
1 Dept. of Materials Eng., University of Tokyo, Tokyo Japan, 3 SPring-8, National Inst. of Materials Science, Sayo Japan, 2 Nano System Functionality Center, National Inst. of Materials Science, Tsukuba Japan
An attempt to in-situ electrochemical polarization measurements has been made to analyze the local nonstoichiometry modulation of Cu2S in the neighboring region of the blocking electrode, in order to verify the nonstoichiometry-induced carrier modfication model for gapless-type two-An attempt to in-situ electrochemical polarization measurements has been made to observe the local nonstoichiometry modulation of Cu2S in the neighboring region of the blocking electrode, in order to verify the nonstoichiometry-induced carrier modfication model for gapless-type two-probe atomic switch using Cu2S. An asymmetric Hebb-Wagner type electrochemical cell, of which construction is expressed as Cu (Reversible electrode)/Cu2S/Pt (Blocking electrode), is used for the experiment at BL-15XU in SPring-8 facility. A marked band bending was observed just below the critical applied potential for the metallic Cu precipitation in addition to a chemical shift of both Cu2p and S1s orbital. In contrast, in-situ measurement using coulometric titration cell composed of Cu/RbCu4Cl3I2/Cu2S have shown none of such broadening while a non-linear chemical shift is observed. The comparison of these PES data suggest a possible reason for the band bending as the steep band bending by the nonstoichiometry modulation because of the supersaturation. Further attempt to oxide atomic switch system will be presented and discussed.
Artur Braun Empa – Swiss Federal Laboratories for Materials Testing and Research
Jinghua Guo Lawrence Berkeley National Laboratory
Randall E. Winans Argonne National Laboratory
Helmut Schober Institut Max von Laue - Paul Langevin (ILL)
W3: H2 Storage and Hydrogen in Solids I
Wednesday AM, April 07, 2010
Room 3004 (Moscone West)
9:30 AM - W3.1
Synchrotron Powder Diffraction Simplified: Introducing the High-resolution Diffractometer 11-BM at the Advanced Photon Source.
Matthew Suchomel 1 , Lynn Ribaud 1 , Robert Von Dreele 1 , Brian Toby 1 Show Abstract
1 Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois, United States
Synchrotrons have revolutionized powder diffraction. They make possible the rapid collection of data with tremendous resolution and a superb signal to noise ratio. The high penetration and wide Q range afforded by high energy light sources like the Advanced Photon Source (APS) even allow synchrotrons to make inroads into territory that previously demanded neutron scattering techniques. Despite all these advances, still relatively few researchers utilize synchrotrons for their powder diffraction experiments.To help address this, the 11-BM synchrotron powder diffractometer at the APS provides users with world-class data via a convenient mail-in service or through on-site experiments. This instrument offers resolution unmatched in North America (ΔQ/Q ~ 2×10-4). With both vertical and horizontal beam focusing capabilities and a detection system consisting of twelve perfect crystal analyzers, the diffractometer can collect a superb pattern suitable for Rietveld analysis in one hour or less. Users of the unique 11-BM rapid access mail-in program typically receive their high-resolution data via email within two weeks of sample receipt at the APS.This presentation will introduce potential users to 11-BM and its associated mail-in program. The performance and capabilities of the current instrument will be discussed. Currently the instrument is equipped with a robotic arm for automated sample changes, and features several sample environments. This presentation will walk would-be users though the simple steps required to submit their own samples via the 11-BM mail-in program and describe the additional options available to on-site users. Examples from previous work by 11-BM users and beamline staff will demonstrate how your research can benefit from high-resolution synchrotron powder diffraction.More information about 11-BM and its mail-in program can also be found on online at http://11bm.xor.aps.anl.gov.
9:45 AM - **W3.2
Combined Gravimetric and Neutron Powder Diffraction Studies of Hydrogen Storage Materials.
Bill David 1 2 , Martin Jones 2 1 , Peter Edwards 2 Show Abstract
1 ISIS Facility, STFC, Chilton United Kingdom, 2 Inorganic Chemistry Laboratory, University of Oxford, Oxford United Kingdom
One of the greatest technological hurdles preventing the widespread development of the hydrogen economy is the lack of a viable hydrogen storage medium for transportation. The storage of hydrogen gas in solids has the potential to address this key requirement - such a store should possess a high capacity (with a system capacity ideally in excess of 5wt% hydrogen), a low desorption temperature of around 120°C, and a complete reversibility of the absorption/desorption cycle. These factors are intimately linked to the crystal structure of any solid state storage material, so that a full structural description coupled with an in-depth investigation of the physical-chemical properties of the absorption/desorption process are necessary to fully understand, and hence properly optimize, the mechanism of hydrogenation and dehydrogenation. To undertake these studies, we have designed and commissioned apparatus that allows neutron diffraction studies to be performed simultaneously with thermogravimetric analysis. In this presentation, we describe experiments performed with this apparatus, the Intelligent Gravimetric Analyzer in conjunction with Neutron diffraction (IGAn). This work was undertaken as a joint project between the Rutherford Appleton Laboratory, Chilton, Didcot (UK) and Hiden Isochema Ltd. The IGAn comprises a microbalance housed in a stainless steel vessel that can be used on neutron powder diffractometers at ISIS. The IGAn thus combines two techniques, neutron powder diffraction and gravimetric analysis, that are among the most important for characterization of hydrogen storage solids. Taken simultaneously, these two techniques give valuable information on both the structural changes and the mechanism and kinetics of hydrogenation and dehydrogenation of solid state hydrogen stores. Various case-studies, including the lithium amide/ lithium imide system, will be described that have been performed on the GEM and HRPD diffractometers at the ISIS pulsed neutron source, Rutherford Appleton Laboratory, UK.
10:15 AM - W3.3
Quaternary Ammonium Borohydride Adsorption in Mesoporous Silicate MCM-48.
Michael Wolverton 1 2 , Luke Daemen 1 , Monika Hartl 1 , Abhijit Bhattacharyya 2 Show Abstract
1 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 2 Applied Science, University of Arkansas at Little Rock, Little Rock, Arkansas, United States
Inorganic borohydrides have a high gravimetric hydrogen density but release H2 only under energetically unfavorable conditions. Surface chemistry may help in lowering thermodynamic barriers, but inclusion of inorganic borohydrides in porous silica materials has proved hitherto difficult or impossible. We show that borohydrides with a large organic cation are readily adsorbed inside mesoporous silicates, particularly after surface treatment. Thermal analysis reveals that the decomposition thermodynamics of tetraalkylammonium borohydrides are substantially affected by inclusion in MCM-48. Inelastic neutron scattering (INS) data show that the compounds adsorb on the silica surface. Evidence of pore loading is supplemented by DSC/TGA, XRD, FTIR, and BET isotherm measurements. Mass spectrometry shows significant hydrogen release at lower temperature from adsorbed borohydrides in comparison with the bulk borohydrides. INS data measured for partially decomposed samples indicates that the decomposition of the cation and anion is likely simultaneous. Additionally, these data confirm the formation of Si-H bonds on the silica surface upon decomposition of adsorbed tetramethylammonium borohydride.
10:30 AM - W3.4
NaBX4-MgX2 Composites (X: D,H) Investigated by in situ Neutron Diffraction.
Daphiny Pottmaier 1 , Sebastiano Garroni 2 , Michella Brunelli 3 , Alberto Castellero 1 , Enric Menendez 4 , Gavin Vaughan 5 , Maria Baro 2 , Marcello Baricco 1 Show Abstract
1 Chimica IFM, Universita di Torino, Turin Italy, 2 Fisica, Universidad Autonoma de Barcelona, Barcelona Spain, 3 D20, Institut Laue-Langevin, Grenoble France, 4 Ion Beam Physics and Materials Research, Forschungszentrum Dresden-Rossendorf, Dresden Germany, 5 ID11, European Synchrotron Radiation Facility, Grenoble France
Complex hydrides (e.g.NaBH4) combined with metal hydrides (e.g.MgH2) is considered a primary class of solid state hydrogen storage materials, the so-called Reactive Hydride Composite (RHC). In spite of drawbacks such as unfavourable thermodynamics and poor kinetics in the dehydrogenation reaction of single hydrides, enhancements may occur in RHCs by nanostructuring of reactant phases and formation of more stable product phases (e.g.MgB2) which lower overall reaction enthalpy and allows reversibility. One potential system is based on ball milling NaBH4 and MgH2 together in a 2:1 molar ratio which can store considerable amounts of hydrogen by weight (up to 7.8wt%). The corresponding desorption reaction 2NaBX4+MgX2 -> MgB2+2NaX+4X2 is assessed by means of in-situ neutron diffraction with different combinations of hydrogen and deuterium on X position. Desorption reaction is established to begin at temperatures as low as 250°C due to joint effects of nanostructured MgX2 and its destabilization by NaBX4. Moreover, successive MgB2 formation along with NaBH4 dehydrogenation is shown to proceed at temperatures higher than 350°C. Due to high scattering of hydrogen element, a direct correlation with H/D desorption reactions is found by the study of the background profile of neutron diffraction patterns in function of temperature. Combined use of hydrogen and deuterium analysed by neutron radiation added insights in the reaction mechanism of this system.
10:45 AM - W3.5
Neutron Scattering and First Principles to Characterize Cu/Mg Destabilized Hydrogen Storage Materials.
Maria Braga 1 , Monika Hartl 1 , Michael Wolverton 1 , Hongwu Xu 1 , Yusheng Zhao 1 , Luke Daemen 1 Show Abstract
1 , LANSCE-LC, LANL, Los Alamos, New Mexico, United States
The pioneering work of Reilly and Wiswall (Inorg. Chem., 1967) on hydrogen storage in Cu2Mg provides the first clear example of destabilization. CuMg2 was reversibly hydrogenated to 3/2MgH2 + 1/2Cu2Mg with an equilibrium pressure of 1 bar at 240 °C. This temperature is ~ 40 °C lower than T(1 bar) for pure MgH2. Nevertheless, since CuMg2 does not form a hydride, the referred work was set aside until very recently. The current search for an on-board hydrogen storage material led to a point where only a system of up to 4 elements will cover all specifications, and this with difficulty. A destabilization strategy then becomes a viable, attractive solution.CuMg2 has an orthorhombic crystal structure (Fddd). However CuLixMg2-x (x = 0.08) has a hexagonal crystal structure (P6222), just like NiMg2 -a compound known for its hydrogen storage properties. NiMg2 absorbs up to 3.6 wt% of hydrogen, at 1 bar and 282 °C (555 K). In spite of the fact that the percentage of H2 absorbed by NiMg2 is enough to propitiate practical applications, the temperature at which the alloy desorbs hydrogen is much too high for current applications. Still, the alloy can be found in practical applications when added to other elements/alloys. A comparison between the phase diagrams of the systems Cu-Mg and Ni-Mg shows that these binary systems form compounds with similar stoichiometry. NiMg2 is formed by peritectic reaction of the elements at 759 °C (1032 K) and CuMg2 at 568 °C (841 K) by congruent melting. The presence of Li lowers even further the melting point of CuMg2. Since the energy of formation of the hydride is related to that of the primary alloy, it was hypothesized that CuLixMg2-x might also be a hydrogen storage material similar to NiMg2. Presumably, its advantage would be that it would release hydrogen at a lower temperature (possibly close to room temperature).Preliminary studies at the Los Alamos Neutron Scattering Center showed that CuLixMg2-x might absorb approximately 5.3 wt% H for an equilibrium pressure of approx. 27 bar at 200 °C. DSC experiments show that a considerable amount of hydrogen can be released at T < 100 °C. If these results are confirmed, this will mean that, not only CuLixMg2-x absorbs a considerable amount of hydrogen, but also will probably release it at a temperature in the range of 50 to 200 °C, where applications are easier to develop. Hence it should be possible to use this alloy with fuel cells or in batteries. It was also observed that a sample containing CuMg2 could release hydrogen at 180 °C ≤ T ≤ 205 °C, probably meaning that the presence of CuLixMg2-x will make MgH2 to release hydrogen at an even lower temperature. In this work we have characterized Cu-Li-Mg (Li, B, Al, Ti) hydrogen storage systems and its thermodynamic properties by means of neutron scattering, first principles calculations, and other complementary techniques.
11:00 AM - W3: Hydrogen I
11:30 AM - W3.6
High-intensity Neutron Total Scattering Instrument (NOVA) for Structural Studies of Hydrogen Storage Materials at J-PARC.
Toshiya Otomo 1 , Kentaro Suzuya 2 , Masakatsu Misawa 1 , Naokatsu Kaneko 1 , Hidetoshi Ohshita 1 , Toshiharu Fukunaga 3 , Keiji Itoh 3 , Kazuhiro Mori 3 , Masaaki Sugiyama 3 , Yasuo Kameda 4 , Toshio Yamaguchi 5 , Koji Yoshida 5 , Yukinobu Kawakita 6 , Kenji Maruyama 7 , Shinichi Shamoto 2 , Shinichi Takata 2 , Setsuo Satoh 1 , Suguru Muto 1 , Junichi Suzuki 1 , Takashi Kamiyama 1 , Susumu Ikeda 1 , Yoshiji Yasu 1 , Kazuo Nakayoshi 1 , Hiroshi Sendai 1 , Shinichi Itoh 1 Show Abstract
1 Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki, Japan, 2 , Japan Atomic Energy Agency, Tokai, Ibaraki, Japan, 3 Research Reactor Institute, Kyoto University, Kumatori, Osaka, Japan, 4 Faculty of Science, Yamagata University, Yamagata, Yamagata, Japan, 5 Faculty of Science, Fukuoka University, Fukuoka, Fukuoka, Japan, 6 Faculty of Science, Kyushu University, Fukuoka, Fukuoka, Japan, 7 Faculty of Science, Niigata University, Niigata, Niigata, Japan
Structure analysis with the atomic Pair Distribution Function (PDF) is now widely used for materials research. Pulsed neutron sources are unique for total scattering measurement to obtain PDF since they provide short-wavelength neutrons effectively, which is important to measure reliable high-Q diffraction data. High-intensity total scattering instrument (NOVA) is a new total diffractometer for disordered materials installed at J-PARC. By utilizing a broadband width of neutron wavelength, it will cover a wide Q-range (0.01 Å-1 < Q < 100 Å-1). NOVA will also be used as a very intense powder diffractometer since its Q-resolution is about 0.35 % at back scattering detectors. These features provide high quality diffraction pattern in absolute scale with reasonable resolution for PDF analysis as well as Rietveld refinement. Also, with the low Q data, larger scale structure and/or fluctuations will be observed. Typical measurement time is expected to be several minutes for full Q-range measurement. Based on these features of NOVA, studies of hydrogen storage mechanism will be intensively focused. In-situ measurements of hydrogen absorbing/desorbing process are planned to understand local structural changes in hydrogen storage materials. NOVA started its commissioning in the end of May 2009. Since then, measurements of diamond powder, silica glass and so on were made and static structure factors, S(Q), were obtained in absolute values successfully. In this talk, the performance expected from these commissioning will be presented. Concepts and ideas for structural studies of hydrogen storage materials will be also presented such as detector arrangements and an inelastic measurement option. This research is supported by NEDO (New Energy and Industrial Technology Department Organization) under "Advanced Fundamental Research Project on Hydrogen Storage Materials"
11:45 AM - W3.7
Structure and Hydrogen Storage Properties of Lithium Amidoborane-Ammonia Borane Complex.
Guotao Wu 1 , Chengzhang Wu 1 , Ping Chen 1 Show Abstract
1 , Dalian Institute of Chemical Physics, Dalian, Liaoning, China
The crystal structure of Lithium Amidoborane-Ammonia Borane complex(LiABAB)was then solved using the combined direct space simulated annealing method and first-principles calculations. LiABAB is of the monoclinic structure (space group P21/c)with lattice constants a = 7.0536(9)Å, b = 14.8127(20)Å, c = 5.1315(7)Å, beta= 97.491(5)°. LiABAB can released 2 equiv. H2 below 100 °C. Additional 3 equiv. H2 can be released if the temperature further increases to 228 °C.The dehydrogenation of LiABAB leaded to the formation of BN, Li3BN2 and LiBH4.
12:00 PM - **W3.8
Energy Materials Research Using Neutron Scattering: An Australian Perspective.
Robert Robinson 1 Show Abstract
1 Bragg Institute, Australian Nuclear Science & Technology Organisation, Menai, New South Wales, Australia
In 2006, two major new research facilities started up in Australia: the Australian Synchrotron (a third-generation 3-GeV machine) and the OPAL Research Reactor (a 20-MW medium-flux reactor). Approximately ten beam lines are now operating, or are under construction, at each facility, with energy materials a focus at both. In my talk, I will focus on the work performed at the OPAL reactor, on a range of energy materials including: hydrogen storage, clathrates, batteries and materials for nuclear power applications.
12:30 PM - W3.9
Ex-situ and in-situ Neutron Radiography Investigations of the Hydrogen Uptake of Nuclear Fuel Cladding Materials During Steam Oxidation at 1000°C and Above.
Mirco Grosse 1 , Eberhard Lehmann 2 Show Abstract
1 Institute for Material Research, Karlsruhe Institute of Technology, Karlsruhe Germany, 2 Department of Spallation Neutron Source, Paul Scherrer Institute , Villigen Switzerland
The most important accident management measure to terminate a severe accident transient in a Light Water Reactor (LWR) is the injection of water to cool down the uncovered degraded core. The combination of hot fuel rods and steam results in a strong exothermic oxidation reaction connected with a sharp increase in temperature, hydrogen production and fission product release. Free protons (hydrogen) are produced in the steam oxidation reaction. They can recombine to H2 gas and be released or they can diffuse through the growing oxide layer and be absorbed by the β-Zr phase. Whereas the released hydrogen gives the risk of a hydrogen detonation in the reactor environment, the absorbed hydrogen results in a shift of the time scale of the hydrogen release and in a reduction of toughness. The results of neutron radiography investigations will be presented in this paper. At first, the method will be introduced and the calibration of the method is described. A linear dependence of the total macroscopic neutron cross section in respect to the hydrogen to zirconium atomic ratio was found, It can be explained by a theoretical interpretation. The results of ex-situ experiments at small cladding segments from separate tests and with samples withdrawn from large scale severe accident simulation tests will be given. The dependence on temperature and time will be discussed for various Zr-Sn and Zr-Nb alloys commonly applied for fuel rod claddings. For compact oxide layers at Zr-Sn alloys the hydrogen concentration reaches a maximal value after short time. Then it decreases with time according to a power of -1/4 dependence. A theoretical model describing this behaviour has been developed and is presented in the paper. A different time dependence of the hydrogen concentration was found for the Zr-Nb alloys. The oxide layer morphology has a strong influence on the. Hydrogen uptake. A crack structure is formed due to the tetragonal to monoclinic phase transformation (known as “breakaway effect”) at temperatures of around 1000°C and results in an about one order of magnitude higher hydrogen concentration in the remaining metal. The mechanism of the “hydrogen pump effect” of open cracks in the oxide will be explained.A reaction furnace with a windows transparent for neutrons was constructed and commissioned in 2008. The first in-situ investigations give information about the first stage of the hydrogen uptake and about details of the processes occurring during the breakaway effect.
12:45 PM - W3.10
Regeneration of AlH3 Studied With Raman and Infrared Spectroscopy.
David Lacina 1 , Yusuf Celebi 1 , James Wegrzyn 1 , Jason Graetz 1 Show Abstract
1 Energy Sciences and Technology, Brookhaven National Lab, Upton, New York, United States
Aluminum hydride compounds are known to exhibit a 10% by weight hydrogen storage capacity that makes them suited for technologies that require hydrogen as a fuel, such as PEM fuel cells. The current challenge associated with this material is how to regenerate the hydride from the spent fuel and H2 gas. We employ a two-step process to regenerate the hydride compound which first requires the formation of a stable aluminum hydride adduct using a tertiary amine. This is followed by a second step consisting of adduct separation and hydride recovery.The alane amines that are formed by this two-step process tend to decompose at high temperature (> 150°C), where the AlH3 is unstable and favors decomposition into aluminum and H2 gas. An additional step involving transamination is required to create a less stable adduct that is easier to separate. For this purpose, triethylamine (TEA) was used to replace the amine in the alane amine adduct to form a less stable adduct that can be separated into AlH3 and TEA by heating to 75°C under a nitrogen sweep (J. H. Murib et al., U.S. patent 3,642,853, 1972.). The conceptual regeneration procedure for AlH3 is shown below:Al* + NR3 + 3/2H2 → AlH3-NR3 + TEA → AlH3-TEA + NR3↑ → AlH3 + TEA↑ The first step in the regeneration of AlH3 involves the formation of an alane amine (AlH3-NR3) from spent fuel. We present results which show that adducts of AlH3 can be formed by hydrogenation of catalyzed aluminum, by adding 2 mol% titanium, in a liquid solvent at low pressures using one of several different tertiary amines. An important part of developing and understanding new materials requires some structural knowledge. Raman and infrared spectroscopy was performed on the products of these reactions to better understand the structure of the alane amines that are formed, as well as the reactions that take place during hydrogenation. Many of the alane amines created in the regeneration process can be formed as either solids, with poorly known structures, or alane containing liquids depending upon the tertiary amine, solvent, and formation conditions employed. A vibrational analysis of the regeneration products performed with Raman and infrared spectroscopy is presented and will help clarify the molecular and vibrational structures of these alane amine adducts.
W4: H2 Storage and Hydrogen in Solids II
Wednesday PM, April 07, 2010
Room 3004 (Moscone West)
2:30 PM - W4.1
Nanostructured Metal Hydrides for Hydrogen Storage Studied by in situ Synchrotron and Neutron Diffraction.
Volodymyr Yartys 1 2 , Roman Denys 1 , Jan Petter Maehlen 1 , Colin Webb 3 , Evan Gray 3 , Tomas Blach 3 , Andrey Poletaev 1 2 , Jan Ketil Solberg 2 , Olivier Isnard 4 Show Abstract
1 , IFE, Kjeller Norway, 2 , NTNU, Trondheim Norway, 3 , Griffith University, Brisbane, Queensland, Australia, 4 , CNRS, Grenoble France
Recent R&D on hydrogen storage have resulted in a new method, “hybrid” H storage, yielding improved by up to 50 % overall H storage system efficiency. In this work we have focused on metal hydrogen systems where one can significantly increase hydrogen storage capacity of the MH on application of high H2 pressures. H storage capacities of the MH suitable for such systems are highly pressure-dependent, when pressures increase to a few hundred bar. High equilibrium hydrogen pressures result in low hydrogenation enthalpies, assisting in achieving high rates of heat exchange during the H loading. Kinetics and mechanism of the phase-structural transformations were studied at the D1B, ILL by in situ PND studies of metal-hydrogen interaction at D2 pressures reaching 1000 bar. High pressures, were generated by use of multistage, heat-based deuterium intensifier. The systems studied included Al-modified Laves-type C15 ZrFe2-xAlx intermetallics with x = 0.02; 0.04 and 0.20. SR XRD measurements showed that Al substitution for Fe leads to a slight expansion of the unit cells. Deuteration showed a very fast kinetics of H/D exchange and resulted in increase of the unit cells volumes reaching 23.5 % for ZrFe1.98 Al0.02D2.9(1). D content, hystheresis of H uptake and release, unit cell expansion and stability of the hydrides systematically change with Al content. D atoms exclusively occupy the Zr2Fe2 tetrahedra. Observed interatomic distances, Zr-D = 2.01-2.07; (Fe,Al)-D=1.75 Å, do not ruled out a possibility of occupancy of the Al-substituted sites. Magnetic moments of Fe slightly increase from the alloy (RT; 1.9 mB) to the corresponding deuteride (RT; 2.2 mB).A different, complementary approach to the development of H storage systems is based on the hydrides of light elements, first of all the Mg-based ones. Time resolved in situ synchrotron X-ray diffraction (SR XRD; 20-400°C; 0-50 bar H2) studied were performed at the SNBL, ESRF. Reactive ball milling in hydrogen (HRBM) allowed synthesis of the nanostructured hydrides of: (a) Mg metal; (b) eutectic alloy Mg8Mm20Ni; Mg+Mg2Ni+MmMg12; (c) LaMg12; (d) Mg-C; (e) Mg-V and Mg-V-C. The experimental parameters (PH2, T, energy of milling, ball / sample ratio and balls size), significantly influence rate of hydrogenation. The studies confirmed (a) a completeness of hydrogenation of Mg into MgH2; (b) indicated a partial transformation of the originally formed beta-MgH2 into a metastable gamma-MgH2 (a ratio beta/gamma was 3/1); (c) yielded the crystallite size for the main hydrogenation product, beta-MgH2, as close to 10 nm. The materials containing hydride-forming additives (Mg8Mm20Ni and V-containing composites) showed decreased temperatures of hydrogen vacuum desorption and fast subsequent rates of rehydrogenation. Influence of the additives to Mg on the structure and hydrogen absorption / desorption properties and cycle behaviour of the composites will be discussed.
2:45 PM - W4.2
Magnetic State in Iron Hydride Under Pressure Studied by X-ray Magnetic Circular Dichroism at the Fe K-edge.
Naoki Ishimatsu 1 , Yasuharu Matsushima 1 , Hiroshi Maruyama 1 , Takao Tsumuraya 2 , Tamio Oguchi 2 , Kenichi Takemura 3 , Takahiro Matsuoka 4 , Masaichiro Mizumaki 4 , Naomi Kawamura 4 Show Abstract
1 , Grad. Sch. of Sci, Hiroshima Univ., Higashi-Hiroshima Japan, 2 , ADSM, Hiroshima Univ., Higashi-Hiroshima Japan, 3 , NIMS, Tsukuba Japan, 4 , JASRI/SPring-8,, Kouto, Sayo Japan
Since the discovery of iron hydride (FeH) [1,2], the effects of hydrogenation on crystal structure and magnetic property in FeH have attracted great interest. FeH can be synthesized by a reaction of Fe metal with hydrogen fluid under 3.5 GPa. Hydrogenation gives rise to a structural transition from bcc-Fe to double-hcp (dhcp) FeH accompanied with a large lattice expansion . Furthermore, FeH is a ferromagnet , so that the transition markedly contrasts with the ferromagnetic bcc-Fe→nonmagnetic hcp-Fe transition appearing at 14 GPa by use of a standard pressure transition medium. To understand the stability of ferromagnetic state in FeH, modification in the electronic structure due to the hydrogenation is an important issue. Here we report pressure dependence of the magnetic state in FeH up to 27 GPa, which was determined by X-ray magnetic circular dichroism (XMCD) at the Fe K-edge. In this study, hydrogen effect on the magnetic state was also investigated. XMCD is a spectroscopic technique using the synchrotron radiation, which provides the element-selective and orbital-specific information about ferromagnetic sample. The XMCD experiments were carried out using the helicity-modulation method on the beamline 39XU at SPring-8. A tiny foil of Fe was loaded into a diamond-anvil cell together with hydrogen fluids. The measurement was done at room temperature.In the pressure range of 3.3 GP〈P〈3.8 GPa, a drastic change in the XMCD spectrum was observed, so that the transition from bcc-Fe to dhcp-FeH occurs within the narrow pressure range. The residual XMCD signal observed at P≥3.8 GPa indicates that FeH remains ferromagnetic state. The XMCD profile of FeH is characterized by a large negative peak near the absorption edge, and it is clearly different from a dispersion-type profile of bcc-Fe. The observed change in XMCD is related to the hydrogen effect on the electronic structure. The XMCD profile for FeH is probably ascribed to the 3d electronic state classified as strong ferromagnetism. On the other hand, the 3d electronic state in bcc-Fe is classified as weak ferromagnetism. When the pressure increases more up to 27 GPa, the integrated intensity is gradually reduced to about 1/5 of that at 3.8 GPa. Critical pressure Pc, where the ferromagnetic state disappears, is estimated to be Pc~29.5 GPa by extrapolation from the pressure variation. Therefore, the ferromagnetic state in FeH is more stable under pressure than that in pure Fe. It is successfully demonstrated that the hydrogenation induces the strong influence on the electronic- and magnetic states in FeH.  V.E. Antonov et al., Sov. Phys. Dokl. 25, 490 (1980) V.E. Antonov, J. Alloys Compd., 330-332, 110 (2002) J.V. Badding et al., Science, 253 421 (1991)
3:00 PM - W4.3
Kinetics Study of Methane Hydrates in Dynamic-DAC.
Jing-Yin Chen 1 , Choong-Shik Yoo 1 Show Abstract
1 , Institute for Shock Physics and Department of Chemistry, Washington State University, Pullman, Washington, United States
Understanding the high-pressure kinetics associated with the formation of methane hydrates is critical to the practical use of the most abundant nature energy resource. In this study, we have studied, for the first time, the kinetics of the formation and phase transitions of methane hydrates under high pressures over a large range of compression rates and pressures, using dynamic-Diamond Anvil Cell (d-DAC) coupled with a high-speed camera and a confocal micro-Raman spectroscopy. At slow compression rates (< 0.1 GPa/s) and below ~1.0 GPa, methane hydrates are formed by forming water clathrates and concurrently capturing methane gas molecules. On the other hand, at high compression rates (>1 GPa/s) and beyond 1 GPa, water molecules solidify, instead, because of a relatively slow rate of hydrate formation and a fast solidification of water. We observed a large pressure hysteresis in both the formation and the decomposition processes of methane hydrates, which likely arises from high (meta) stability of methane hydrates.Below 10 GPa, methane hydrates exist in three polymorphs, sI, sII, and sH, with characteristic Raman spectra and visual appearance. The sI and sII phases of methane hydrates have similar crystalline textures and optical transparencies, yet the sH phase has a substantially darker “dirty-look” texture. We have examined the dynamics of the sI-sII transition over the compression rates of 0.0008-0.1 GPa/s and pressures of 0.6-1.5 GPa and of the sII-sH transition over the compression rates 0.002-0.9 GPa/s and pressures of 1.8-2.4 GPa. The results indicate a similar dynamics governing the forward and backward transitions between sI and sII phases, but very different ones between sII and sH phase transitions. That is, the sII-to-sH transition occurs substantially faster than the reverse process. In this talk, we will discuss about chemical mechanisms of the formation and phase transitions of methane hydrates, following a brief description of dynamic-DAC.
3:15 PM - W4.4
Ammonia Borane and a New Ammonia Borane-hydrogen Compound at High Pressure.
Yu Lin 1 , Vadym Drozd 2 , Jiuhua Chen 2 , Luke Daemen 3 , Ho-kwang Mao 4 , Wendy Mao 1 5 Show Abstract
1 Geological and Environmental Sciences, Stanford University, Stanford, California, United States, 2 , Mechanical and Materials Engineering, Florida International University, Miami, Florida, United States, 3 , Los Alamos Neutron Science Center, Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 4 , Geophysical Laboratory, Carnegie Institution of Washington, Washington, District of Columbia, United States, 5 , Photon Science, SLAC National Accelerator Laboratory, Menlo Park, California, United States
Ammonia borane (AB), NH3BH3, is a novel hydrogen storage material with its high gravimetric and volumetric hydrogen density compared to other candidates. High pressure studies can improve our understanding of structural relationships in hydrogen storage materials and provide guidance for designing improved storage materials. We investigated the effect of pressure on the bonding in AB using Raman spectroscopy up to 22.3 GPa in a diamond anvil cell. Two new transitions were observed at approximately 5 and 12 GPa. Vibrational frequencies for the modes of the NH3 proton donor group exhibited negative pressure dependence, which is consistent with the behavior of conventional hydrogen bonds, while the vibrational frequencies of the BH3 proton acceptor group showed positive pressure dependence. The observed behavior of these stretching modes supports the presence of dihydrogen bonding at high pressure. The observation that BH3 and NH3 bending modes showed an increase in spectral complexity with increasing pressure together with a discontinuity in dν/dP also suggests rotational disorder in this molecule. We also studied AB in the presence of excess hydrogen (H2) pressure and discovered a novel solid phase, AB(H2)x, where x ~ 1.3 - 2. The new AB-H2 compound can store an estimated 8 - 12 wt% molecular H2 in addition to the chemically bonded H2 in AB. This phase formed slowly at 6.2 GPa, but the reaction rate could be enhanced by crushing the AB sample to increase its contact area with H2. X-ray diffraction of the new phase indicates that it has a different crystal structure from pure AB at the equivalent pressure. The compound has two Raman H2 vibron peaks from the absorbed H2 in the new phase: one at frequency 70 cm-1 below the free H2 vibron, and the other at higher frequency overlapping with the free H2 vibron at 6 GPa and becoming visible above 8.8 GPa. The splitting of the N-H and B-H stretching modes, as well as the distinct H2 vibrons suggest a strong molecular bonding between AB and H2, and the structural complexity of this new compound. Storage of significant amounts of additional molecular H2 in AB increases the already high hydrogen content of AB. The complex reaction kinetics, bonding variations, and slow reaction rate give hope for designing alternative chemical paths to synthesize and retain the new compound for practical hydrogen storage application.
3:30 PM - W4:Hydrogen II
W5: PEM Fuel Cells and Electrocatalysis
Wednesday PM, April 07, 2010
Room 3004 (Moscone West)
4:00 PM - **W5.1
Neutron Imaging Methods for the Investigation of Energy Related Materials (Fuel Cells, Battery, Hydrogen Storage and Nuclear Fuel).
Eberhard Lehmann 1 , Pierre Boillat 1 Show Abstract
1 NUM, Paul Scherrer Institut, Villigen Switzerland
Novel approaches will play an important role in the world-wide energy supply and consumption. Among the favorite concepts for mobility and local electricity production the electro-chemistry concepts of fuel cells and of improved batteries will raise importance. In this context, also the storage of hydrogen as an energy carrier will get a higher level of consideration. Although some of the mentioned devices and techniques are already in use, the improvement of their performance and reliability is an important issue to introduce them on economic level in competition to other concepts. This talk is focused on the non-invasive investigation of components and materials for fuel cells, batteries and potential hydrogen storage devices. The applied method is neutron imaging which is developed and practiced on high performance level at Paul Scherrer Institute, Switzerland, at the spallation neutron source SINQ. Neutron imaging can provide structural information of samples and systems in two dimensions (radiography) and three dimensions (tomography) and is able to study time-dependent phenomena in a quasi-real time regime. It is the advantage of neutron imaging methods to enable a high contrast to light elements like hydrogen and lithium while the transmission of structural materials like Al, C or even steel is given for thick layers. Therefore, it is an ultimate approach to investigate Polymer Electrolyte Membrane Fuel Cells (PEM-FC) in respect to its water distribution in the membrane region. Different membrane materials are under investigation and the performance is tested under realistic operational conditions while the water distribution is observed.In the case of battery research two major questions are of importance: how the gas production is related to loading/discharging cycles; is there a migration of ions visible during battery operation. Studies in this respect have just started. Different material combinations will be under evaluation. The storage of hydrogen will become more importance when fuel cells and other hydrogen related energy processes will be introduced on broad scale. Not only the gas storage under pressure or low temperature is than an option but the bonding on metals and other chemicals which deliver hydrogen on demand. Materials like zirconium have a high affinity to hydrogen and might be used as storage devices. With the help of neutron imaging methods it is relatively easy to determine the hydrogen uptake and loss under realistic conditions in assemblies of different size. The talk will describe the methods principle, show the layout of the used facilities and gives examples of latest investigations.
4:30 PM - W5.2
Origin of Enhanced Oxygen Reduction Activity on Dealloyed PtCu3 Thin Films.
Ruizhi Yang 1 , Mike Toney 1 Show Abstract
1 , Stanford University, Menlo Park, California, United States
The oxygen reduction activity of the electrochemically dealloyed PtCu3 thin film was studied in 0.1 M HClO4 using a rotating disk electrode (RDE) method. The dealloyed sample showed a ~2.4 fold gain in the specific activity over pure Pt thin film sample. A thick Pt enriched surface layer and Cu depleted interior (bulk ratio of alloying components is different from PtCu3) were shown to be formed in the dealloyed PtCu3 film by synchrotron-based anomalous X-ray diffraction (AXRD). The lattice constant of Pt enriched surface layer is smaller than that of pure Pt and thus induce the compressive lattice strain in the thick surface layer, which is shown to dominate the enhanced catalytic activity of the dealloyed Pt-Cu thin film.
4:45 PM - W5.3
Surface Structure and Electrochemistry of Model Electrocatalysts.
Alexander Brownrigg 1 , Christopher Lucas 1 , Paul Thompson 1 , Michael Cormack 1 , Michael Darlington 1 , Voja Stamenkovic 2 , Dusan Strmcnik 2 , Nenad Markovic 2 Show Abstract
1 Oliver Lodge Laboratory, University of Liverpool, Liverpool United Kingdom, 2 Material Science Division, Argonne National Laboratory, Argonne, Illinois, United States
Since the early days of modern surface science, the main goal in the electrochemical community has been to find correlations between the microscopic structures formed by surface atoms and adsorbates and the macroscopic kinetic rates of a particular electrochemical reaction. The establishment of such relationships, previously only developed for catalysts under ultrahigh vacuum (UHV) conditions, has been broadened to embrace electrochemical interfaces. In early work, determination of the surface structures in an electrochemical environment was derived from ex situ UHV analysis of emersed surfaces. The application of in situ surface sensitive probes, most notably synchrotron based surface x-ray scattering (SXS) and scanning tunneling microscopy (STM) has overcome the “emersion gap” and provided information on potential-dependent surface structures at a level of sophistication that is on a par with (or, even, in advance of) that obtained for surfaces in UHV. In this talk we will describe the application of the synchrotron SXS technique for exploring surface atomic structure in an electrochemical environment in order to understand processes relevant to the development of new materials for energy applications . The focus will not just be on the determination of the atomic structure at the electrochemical interface but will also describe the use of SXS in potentiodynamic measurements where the aim is to correlate, directly, the electrochemical reactivity with atomic-scale structural changes at the electrode surface. Results will be presented for both extended low-index single crystal surfaces and stepped electrode surfaces. The stepped surfaces enable a correlation between reactions on flat terraces to those occurring at well-defined steps. Measurements of various potential-dependent reactions, for example, the oxidation of carbon monoxide and the oxygen reduction reaction (ORR) will be discussed.
5:00 PM - **W5.4
Chemical Mapping of Fuel Cell Membrane Electrode Assemblies by Soft X-ray Spectromicroscopy.
Adam Hitchcock 1 , Dmitri Bessarabov 2 Show Abstract
1 BIMR, McMaster University, Hamilton, Ontario, Canada, 2 , Automotive fuel Cell Cooperation, Burnaby, British Columbia, Canada
Soft X-ray scanning transmission X-ray microscopy (STXM) is a synchrotron based technique which provides speciation through near-edge X-ray absorption spectroscopy, and quantitative chemical and orientation mapping at 30 nm spatial resolution . It was applied at the C 1s, N 1s, O 1s, Co 2p and F 1s edges to the membrane electrode assemblies (MEAs) of hydrogen-based polymer electrolyte membrane (PEM) fuel cell before and after being subjected to a specific drive cycle simulating the operation of a fuel cell vehicle (FCV). The catalyst coated membranes (CCMs) were extracted from the MEAs and 100 or 300 nm thick microscopy samples of CCM cross-sections were prepared at various positions along the CCM using embedding and ultramicrotomy. Post-mortem studies of CCM samples were carried out to determine the degree of Pt dissolution in the membrane. STXM results were complemented by SEM and TEM imaging and X-ray fluorescence analysis (EDX). All STXM measurements were made at beamline 5.3.2 of the Advanced Light Source (Berkeley, CA).This study provided information on: (1) morphology and chemistry of platinum particles in the membrane, (2) chemical differences between the beginning-of- life (BOL) and end-of-life (EOL) samples, (3) evaluating STXM versus EDX in TEM and SEM as a probe of the distribution of Co across the CCM, (4) porosity of the CCM.It was demonstrated that STXM is a useful technique for studies of MEA components of a fuel cell. STXM can map Co in the cathode and membrane to low levels (~100 ppm). Detailed, spatially resolved spectroscopy at multiple core level edges gave insights into the chemical changes that occur in association with component degradation of fuel cells through automotive operation. Several different approaches to mapping porosity were explored.Research funded by AFCC and NSERC. H. Ade and A.P. Hitchcock, Polymer 49 (2008) 643
5:30 PM - W5.5
Activation of O2 by Gold Nanoparticles? In situ Ambient-pressure X-ray Photoelectron Spectroscopy Study.
Peng Jiang 1 , Soeren Porsgaard 2 , Ferenc Borondics 3 , Mariana Koeber 1 , Alfonso Caballero 1 , Hendrik Bluhm 3 , Flemming Besenbacher 2 , Miquel Salmeron 1 Show Abstract
1 Materials Sciences Division, Lawrence Berkeley National Lab, Berkeley, California, United States, 2 Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Aarhus Denmark, 3 Chemical Sciences Division, Lawrence Berkeley National Lab, Berkeley, California, United States
The interaction of O2 with gold foil and gold nanoparticles grown by vapor deposition on TiO2(110) was studied by in situ ambient-pressure X-ray photoelectron spectroscopy (AP-XPS). No spontaneous dissociation of O2 was observed either on Au foil or on Au nanoparticles up to one atmosphere of O2. X-ray irradiation, however, is very effective in promoting gold oxidation on both surfaces in the presence of O2. These results help reconcile recent conflicting experimental observations regarding the activation of molecular oxygen on Au nanoparticles, which is at the core of their catalytic performance in oxidation reactions.
5:45 PM - W5.6
In-situ Investigations of Pt DENs Using EXAFS During CO Stripping and Oxygen Reduction.
Michael Weir 1 , Sue Myers 1 , Richard Crooks 1 , Anatoly Frenkel 2 Show Abstract
1 Chemistry & Biochemistry, Univ. of Texas @ Austin, Austin, Texas, United States, 2 , Yeshiva University, New York, New York, United States
We have recently used extended x-ray absorbance-fine structure (EXAFS) as a tool to probe the in-situ behavior of small (< 3nm) Pt nanoparticles. The ability to transition from ex-situ to in-situ characterization methods is particularly important for these small particles because such a large portion of their component atoms are on the surface (> 50%). Therefore, they are more sensitive to surface induced structural changes. We have designed a cell which allows us to perform traditional 3-electrode electrochemistry and still measure the nanoparticles using EXAFS. These measurements allow us to correlate previous electrochemical results with ex-situ characterization. So far, we have investigated the behavior of Pt dendrimer-encapsulated nanoparticles (DENs) during CO stripping and the oxygen reduction reaction (ORR).The dendrimer-encapsulation technique is a templating method that allows synthesis of mono- and bi- metallic nanoparticles on the 1-2 nm scale (40-240 atoms). The size of these nanoparticles, particularly with the protective dendrimer, reduces the availability of analytical techniques. EXAFS is well-suited for our system, as the x-rays are unaffected by the dendrimer. Also, the coordination numbers obtained from a first-shell fitting analysis can be used to determine particle diameter in this size regime.The CO stripping process involves the electrochemically induced adsorption and removal of a single monolayer of CO onto a Pt surface. The amount of current passed during the removal is used to determine the electrochemically active surface area of the Pt. Because CO is a strongly binding ligand, and known to anneal and/or agglomerate larger particles, we have been concerned that the CO stripping process would cause changes in the size and structure of the DENs, invalidating any comparison between previous characterization work and the electrochemical data. Accordingly, we have used EXAFS to probe the structure of these Pt DENs during the CO stripping process. The reducing potential used to adsorb the CO layer is shown to further reduce the Pt nanoparticles, while the CO has no significant effect on the state of these particles. That is, the dendrimer is able to prevent agglomeration of our Pt nanoparticles during the CO stripping process.The oxygen reduction reaction is another electrochemical reaction which we have previously studied ex-situ. Here we expect to answer the questions of whether the Pt DENs change over the time needed to measure their catalytic ability and whether any transformation is potential dependent. Initial results indicate an irreversible change under catalytic conditions. Regardless of the final conclusions, we have demonstrated the ability to detect structural changes in Pt DENs during electrochemical reactions.
W6: Poster Session
Thursday AM, April 08, 2010
Salon Level (Marriott)
9:00 PM - W6.1
In situ XRD Investigation of Tin Oxide/Multiwalled Carbon Nanotubes Composite Anode for Li-ion Battery.
Abirami Dhanabalan 1 , Kevin Bechtold 1 , Chunlei Wang 1 Show Abstract
1 MME, Florida International University, Miami, Florida, United States
Amorphous tin composite oxide (ATCO) has gained much attraction due to their high theoretical capacity compared to the commonly used graphite anodes. In this work, porous tin oxide/ multiwalled carbon nanotubes (MWCNTs) has been suggested to reduce the drawbacks such as the stress associated with huge volume change during Li-ion insertion / desertion and poor conductivity of tin oxide based electrodes. The samples were prepared using Electrostatic Spray Deposition technique (ESD). Currently the mechanism of operation of these anodes at the micro structural level is not yet fully understood. In order to investigate the correlation between the micro structural changes and electrochemical property, in situ X-ray Diffraction was used. As prepared tin oxide / MWCNTs was used as the anode in 1M lithium bis(perfluoroethylsulfonyl)imide in ethylene carbonate and diethyl carbonate (EC-DEC, 1:1 v/v) electrolyte versus Lithium (counter and reference electrode) in a specially designed test cell. In situ XRD measurements were carried out using XRD D-5000 with Cu-Kα radiation. The sequence of Li-ion insertion mechanism and the micro structural changes were studied during the charge-discharge cycle. The results were compared with pure tin oxide and pure CNT electrodes prepared using the same method.
9:00 PM - W6.10
Real-time and Direct Observation of Hydrogen Absorption Dynamics for Pd Nanoparticles.
Daiju Matsumura 1 , Yuka Okajima 1 , Yasuo Nishihata 1 , Jun'ichiro Mizuki 1 Show Abstract
1 , Japan Atomic Energy Agency, Hyogo Japan
Palladium is known to show high performance for the hydrogen storage because of the small activation barrier for the surface adsorption and the exothermal reaction for the inner absorption. Although it has been established that the H atoms are absorbed into the octahedral vacancies of Pd fcc lattice, the dynamic mechanisms of the hydrogen storage process which consists of the surface adsorption and following inner absorption have not been well understood yet, especially for the case of Pd metal fine particles which sometimes show unique properties of the gas-solid interaction.Pd metal fine particles show the different interaction with hydrogen from the bulk Pd. There is a significant phase boundary between the low-concentrate phase (interstitial phase) and the high-concentrate phase (hydride phase) as for the bulk Pd. On the other hand, the Pd metal fine particles show smooth change between interstitial and hydride phases.In order to understand the size effect of the Pd particles concerning the dynamical hydrogen storage process including surface adsorption and inner absorption, we have observed the Pd K-edge x-ray absorption fine structure (XAFS) spectra with dispersive optics from the viewpoint of the dynamical change of atomic and electronic structures during reaction between Pd particles and H2 gases.XAFS spectra were observed at BL14B1 of SPring-8 by dispersive mode. Laue configuration with Si(422) reflection plane was adopted for bend crystal polychromator. The transmitted x rays were observed by CCD camera (640 x 480, 12 bits) with Gd2O2S(Tb) phosphor. The local structural tran