Abstract

Understanding how the composition and atomic-scale structure of a nanocatalyst changes when it is operated under realistic oxygen reduction reaction (ORR) conditions is essential for enabling the design and preparation of active and robust catalysts in proton exchange membrane fuel cells (PEMFCs). This report describes a study of palladium-alloyed electrocatalysts (PdNi) with different bimetallic compositions, aiming at establishing the relationship between catalyst’s composition, atomic structure, and activity for ORR taking place at the cathode of an operating PEMFC. Ex-situ and in-situ synchrotron high-energy X-ray diffraction (HE-XRD) coupled to atomic pair distribution function (PDF) analysis are employed to probe the structural evolution of the catalysts under PEMFC operation conditions. The study reveals an intriguing composition–activity synergy manifested by its strong dependence on the fuel cell operation induced leaching process of base metals from the catalysts. In particular, the synergy sust...

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