X-rays have wavelengths on the order of atomic dimensions and the ability to penetrate through low atomic number materials.  These attributes make X-ray techniques uniquely suited for the atomic-level characterization of transition metal-containing nano-scale proton exchange membrane fuel cell electrocatalysts in various environments relevant to their catalytic performance in the fuel cell.  These environments include in operando, (i.e., in the actual fuel cell), in situ (i.e., in aqueous electrolyte mimicking fuel cell conditions), and in the ionomer-catalyst-solvent inks used to fabricate fuel cell electrodes.  Examples will be given of the information that can be obtained on the catalysts' atomic structure, oxidation state, and particle size and shape utilizing X-ray absorption spectroscopy, anomalous small-angle X-ray scattering, and ultra-small angle X-ray scattering.  These synchrotron-based X-ray experiments have provided, for example, information on the identity of the active sites in platinum group and non-platinum group metal electrocatalysts, the influence of ink composition and processing on the electrocatalyst composition and particle size, which impacts the available electrochemically active surface area, and the changes in these properties during fuel cell operation.

In situ X-ray absorption and scattering studies of proton exchange membrane fuel cell electrocatalysts

247th National Meeting (2014)

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