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The use of in situ X-ray absorption spectroscopy in applied fuel cell research

: Croze, V.; Ettingshausen, F.; Melke, J.; Söhn, M.; Stürmer, D.; Roth, C.


Journal of Applied Electrochemistry 40 (2010), No.5, pp.877-883
ISSN: 0021-891X
ISSN: 1572-8838
Journal Article
Fraunhofer ISE ()
Energietechnik; Wasserstoff- und Brennstoffzellentechnologie; Wasserstofftechnologie; Brennstoffzellensysteme

For a detailed understanding and systematic optimization of fuel cell systems, in situ studies are an indispensable tool, as they provide information on the catalyst structure in different operation conditions. X-ray absorption spectroscopy (XAS) is in particular suitable for operando investigations, since it does not require ultra high vacuum conditions or long-range order in the sample. Furthermore, it provides in situ information on oxidation state, adsorbed species and catalyst structure, and thus complements ex situ information, e.g. from X-ray diffraction (structure), X-ray photoelectron spectroscopy (oxidation state) and FTIR (adsorbates) nicely. In a spectroelectrochemistry experiment, XAS can be combined with different electrochemical techniques in order to satisfy different needs and scientific aims. Spectra of both a Pt-Ru anode catalyst and a Pt-Co cathode catalyst were recorded at different potentials, while measuring the current-potential characteristics of a single cell. So-called half-cell measurements, where the former fuel cell cathode was used with hydrogen as the reference electrode, were performed in water and ethanol to obtain a more detailed mechanistic insight into the ethanol electrooxidation. From a more industrial point of view, different catalysts were tested with a fast potential cycling protocol simulating rapid load changes in a vehicle.