Investigation of the local catalyst distribution in an aged direct methanol fuel cell MEA by means of differential synchrotron X-ray absorption edge imaging with high energy resolution

Synchrotron X-ray absorption edge imaging with high energy resolution was applied to study aging of fuel cell catalyst materials. The combination of an imaging and a high X-ray energy resolution set-up allows acquiring spatially resolved XAS (XANES and EXAFS) spectra. We analyzed the two-dimensional distribution of Pt and Ru in fresh and aged fuel cell catalysts. Spatially resolved XAS images were taken at the RuK edge and at the PtL3 edge. Taking radiographs above and below the absorption edges provides quantitative information about the thickness of the catalytic materials and additional chemical information. A strong influence of the flow field channels and the structure of the gas diffusion layers on the thicknesses of the catalytic elements were found: a thinner catalyst layer was found below the ribs of the flow field geometries as well as under crossing points of fiber bundles of the woven gas diffusion layers.

[1]  David Sinton,et al.  Dynamic water transport and droplet emergence in PEMFC gas diffusion layers , 2008 .

[2]  J. Goodenough,et al.  Methanol oxidation on unsupported and carbon supported Pt + Ru anodes , 1988 .

[3]  A. Hamnett,et al.  Mechanism and electrocatalysis in the direct methanol fuel cell , 1997 .

[4]  S. Zabler,et al.  High resolution synchrotron-based radiography and tomography using hard X-rays at the BAMline (BESSY II) , 2008 .

[5]  Jack S. Brenizer,et al.  Liquid Water Storage, Distribution, and Removal from Diffusion Media in PEFCS , 2006 .

[6]  H. Gasteiger,et al.  Structure and Chemical Composition of a Supported Pt-Ru Electrocatalyst for Methanol Oxidation , 1995 .

[7]  J. Banhart,et al.  Investigation of the three-dimensional ruthenium distribution in fresh and aged membrane electrode assemblies with synchrotron X-ray absorption edge tomography , 2011 .

[8]  Piotr Zelenay,et al.  Ruthenium Crossover in Direct Methanol Fuel Cell with Pt-Ru Black Anode , 2004 .

[9]  I. Schneider,et al.  Locally Resolved Electrochemical Impedance Spectroscopy in Channel and Land Areas of a Differential Polymer Electrolyte Fuel Cell , 2011 .

[10]  John Banhart,et al.  Synchrotron X-ray tomography for investigations of water distribution in polymer electrolyte membrane fuel cells , 2011 .

[11]  S. Narayanan,et al.  Investigation of Ruthenium Dissolution in Advanced Membrane Electrode Assemblies for Direct Methanol Based Fuel Cell Stacks , 2006 .

[12]  D. Chu,et al.  Methanol Electro‐oxidation on Unsupported Pt‐Ru Alloys at Different Temperatures , 1996 .

[13]  John Banhart,et al.  Investigation of Energy‐Relevant Materials with Synchrotron X‐Rays and Neutrons , 2011 .

[14]  E. Smotkin,et al.  In situ x-ray absorption fuel cell , 2002 .

[15]  H. Gasteiger,et al.  LEIS and AES on sputtered and annealed polycrystalline Pt-Ru bulk alloys , 1993 .

[16]  Shohji Tsushima,et al.  Soft X-ray visualization of the liquid water transport within the cracks of micro porous layer in PEMFC , 2011 .

[17]  Combined local current distribution measurements and high resolution neutron radiography of operating Direct Methanol Fuel Cells , 2009 .

[18]  J. Hazemann,et al.  X-ray absorption near edge structure study of the electro-oxidation reaction of CO on Pt50Ru50 nanoparticles , 1995 .

[19]  Chao-Yang Wang,et al.  Pore-network modeling of liquid water transport in gas diffusion layer of a polymer electrolyte fuel cell , 2007 .

[20]  J. Mergel,et al.  Degradation effects at the methanol inlet, outlet and center region of a stack MEA operated in DMFC , 2011 .

[21]  W. Sugimoto,et al.  Enhanced activity and stability of Pt/C fuel cell anodes by the modification with ruthenium-oxide nanosheets , 2010 .

[22]  Heinrich Riesemeier,et al.  BAMline: the first hard X-ray beamline at BESSY II , 2001 .

[23]  A. Wokaun,et al.  Negative Resistance Values in Locally Resolved Impedance Spectra of Polymer Electrolyte Fuel Cells , 2009 .

[24]  A. A. Kulikovsky,et al.  Numerical simulation of a new operational regime for a polymer electrolyte fuel cell , 2001 .

[25]  W. Kleemann,et al.  Multiwave diffraction theory of magnetic phase gratings and its application to ferromagnetic stripe domains in K2CuF4 , 1982 .

[26]  D. Rolison,et al.  Role of hydrous ruthenium oxide in Pt-Ru direct methanol fuel cell anode electrocatalysts: The importance of mixed electron/proton conductivity , 1999 .

[27]  Brian E. Conway,et al.  Modern Aspects of Electrochemistry , 1974 .

[28]  High resolution synchrotron X-ray investigation of carbon dioxide evolution in operating direct methanol fuel cells , 2009 .

[29]  G. Goerigk,et al.  In situ anomalous small-angle X-ray scattering and X-ray absorption near-edge structure investigation of catalyst structures and reactions , 1996 .

[30]  A. Russell,et al.  X-ray absorption spectroscopy of low temperature fuel cell catalysts. , 2004, Chemical Reviews.

[31]  N. Djilali,et al.  Ex situ visualization of liquid water transport in PEM fuel cell gas diffusion layers , 2006 .

[32]  Chengwei Wu,et al.  Liquid water transport mechanism in the gas diffusion layer , 2010 .

[33]  D. Stolten,et al.  The influence of cathode flow field surface properties on the local and time-dependent performance of direct methanol fuel cells , 2010 .

[34]  Werner Lehnert,et al.  Investigation of water evolution and transport in fuel cells with high resolution synchrotron x-ray radiography , 2007 .

[35]  Alexander Wokaun,et al.  Oscillations in Gas Channels II. Unraveling the Characteristics of the Low Frequency Loop in Air-Fed PEFC Impedance Spectra , 2007 .

[36]  Zhigang Qi,et al.  Open circuit voltage and methanol crossover in DMFCs , 2002 .

[37]  Masahiro Watanabe,et al.  Electrocatalysis by ad-atoms: Part II. Enhancement of the oxidation of methanol on platinum by ruthenium ad-atoms , 1975 .

[38]  John Banhart,et al.  X-ray and neutron imaging – Complementary techniques for materials science and engineering , 2010 .

[39]  Chao-Yang Wang,et al.  Quantification of Liquid Water Saturation in a PEM Fuel Cell Diffusion Medium Using X-ray Microtomography , 2006 .

[40]  I. Manke,et al.  Local Structural Characteristics of Pore Space in GDLs of PEM Fuel Cells Based on Geometric 3D Graphs , 2009 .

[41]  Heinrich Riesemeier,et al.  Investigation of 3D water transport paths in gas diffusion layers by combined in-situ synchrotron X-ray radiography and tomography , 2011 .

[42]  J. Banhart,et al.  In situ Synchrotron X‐ray Radiography Investigations of Water Transport in PEM Fuel Cells , 2009 .

[43]  The influence of gas diffusion layer wettability on direct methanol fuel cell performance: A combined local current distribution and high resolution neutron radiography study , 2010 .

[44]  Robert F. Savinell,et al.  Real‐Time Mass Spectrometric Study of the Methanol Crossover in a Direct Methanol Fuel Cell , 1996 .

[45]  Hubert A. Gasteiger,et al.  Methanol electrooxidation on well-characterized Pt-Ru alloys , 1993 .