A New Approach to Probe the Degradation of Fuel Catalysts Under Realistic Conditions: Combining Tests in a Gas Diffusion Electrode Setup with Small Angle X-Ray Scattering

A new approach for efficiently investigating the degradation of fuel cell catalysts under realistic conditions is presented combining accelerated stress tests (ASTs) in a gas diffusion electrode (GDE) setup with small angle X-ray scattering (SAXS). GDE setups were recently introduced as a novel testing tool combining the advantages of classical electrochemical cells with a three-electrode setup and membrane electrode assemblies (MEAs). SAXS characterization of the catalyst layer enables an evaluation of the particle size distribution of the catalyst and its changes upon applying an AST. The straight-forward approach not only enables stability testing of fuel cell catalysts in a comparative and reproducible manner, it also allows mechanistic insights into the degradation mechanism. In contrast to standard rotating disk electrode measurements or identical location microscopy, typical metal loadings for proton exchange membrane fuel cells (PEMFCs), i.e. 0.2 mgPt cm-2geo, are applied in the GDE and the degradation of the overall (whole) catalyst layer is probed. For the first time, realistic degradation tests can be performed comparing a set of catalysts with several repeats within reasonable time. It is demonstrated that independent of the initial particle size in the pristine catalyst, for ASTs simulating load cycle conditions in a PEMFC, all catalysts degrade to a more or less identical particle size distribution. The presented new approach will help to pave the way to develop improved PEMFC catalysts.