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.
In situ Fuel cells X-ray absorption spectroscopy Spectroelectrochemistry Operando
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Thanks are due to the staff of beamline X1 at HASYLAB, Hamburg, in particular A. Webb and M. Hermann.