With wavelengths on the order of atomic dimensions and the ability to penetrate through low atomic number materials, X-rays are ideal for atomic-level characterization of catalysts ex situ, in aqueous environments mimicking polymer electrolyte fuel cell conditions, and in membrane-electrode assemblies (MEAs) during operation. We are using X-ray absorption spectroscopy, to determine the atomic structure, oxidation state, and d-band vacancy of nanoparticle platinum and non-platinum electrocatalysts and small-angle X-ray scattering (SAXS) to determine particle size distributions. The information from these techniques is correlated with electrochemically-active surface area (ECA) and aqueous dissolution measurements to determine the mechanisms of ECA loss for Pt/C and Pt3Co/C cathode electrocatalysts. Using in situ SAXS, we have, for the first time, observed Pt nanoparticle growth in a cathode of an MEA during potential cycling. In addition, high-resolution X-ray diffraction is being used to study the phase structure of alloy electrocatalysts during catalyst preparation.

In situ X-ray absorption and scattering studies of PEFC cathode electrocatalysts

243rd National Meeting (2012)

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