Deciphering the Atomic-Scale Degradation of Carbon-Supported Platinum–Yttrium Nanoalloys during the Oxygen Reduction Reaction in Acidic Medium

Platinum–yttrium alloys are considered promising candidates to satisfy the challenging requirements for the cathodic oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). Nevertheless, the practical structure–activity-stability trends of these electrocatalysts in the form of carbon-supported nanostructures are poorly understood, especially under the operating conditions. Herein, the properties of carbon-supported Pt x Y nanoalloys were explored during the electrochemical ORR environment, following the atomic-scale degradation steps that the nanoalloys experience during operation. Our results reveal that Pt x Y/C nanoalloys undergo considerable structural modification during the early stage of electrochemical cycling. Moreover, operando techniques identify that, during accelerated stress testing under O2 atmosphere, the majority of nanoalloy degradation occurs during the initial 1000 electrochemical cycles, and is accompanied by a diminished ORR performance. The observed operando structure–activity-stability trends guide further optimization routes for carbon-supported Pt–Y nanoalloys as PEMFC cathode electrocatalysts.