Abstract
Platinum-rare earth nanoalloys have been predicted to be promising proton exchange membrane fuel cell (PEMFC) electrocatalysts for the cathodic oxygen reduction reaction (ORR). However, their implementation in PEMFCs is limited by the challenge of their preparation as carbonsupported nanostructures. Consequently, the practical structure-activity-stability trends for this class of nanoalloys remain largely unexplored. Herein, carbon-supported Pt-Nd nanoalloys as ORR electrocatalysts are described. The physical chemistry of selected electrocatalysts was extensively investigated by means of combined ex situ and operando techniques, which reveal the unique structural dynamics of Pt-Nd nanoalloys in a simulated PEMFC cathode environment. The experimental observations, supported by theoretical calculations, indicate that after initial significant structural modification in the early stage of operation, the ORR activity is mediated in the longer-term by surface compressive strain rather than charge transfer between Pt and Nd. Such key operando structure-activity-stability relations underpin further optimization of carbonsupported Pt-rare earth nanoalloys as fuel cell cathode catalysts.