Harnessing Dynamic Metal‐Oxide Interfaces for Durably Active Fuel Cell Electrocatalysis

While metal-oxide interfaces can profoundly modulate the performance of (electro)catalysts, their dynamic nature under operational conditions remains poorly understood, and a compromise between activity and stability persists as a central challenge. Herein, we reveal a dynamic, "breathing" interface behavior in MO_x/Pt (M = In, Sn, Sb) systems during the cathodic oxygen reduction reaction (ORR) in proton-exchange membrane fuel cells. By constructing well-defined Pt octahedra decorated with ultrathin p-block metal oxide overlayers, we demonstrate that an oxygen-deficient M-Pt interface forms at reducing potentials and improves the ORR activity following a trend of In-Pt > Sn-Pt ∼ Sb-Pt via interfacial charge transfer, while oxidizing potentials generate an oxygen-enriched M-O-Pt structure that effectively suppresses Pt dissolution and improves catalytic durability, particularly with SnO_x overlayers. We further validate that harnessing the dynamic metal-oxide interfaces represents a new and generalizable strategy to break the activity and stability trade-off for a wide range of shaped or non-shaped Pt and Pt-bimetallic catalysts, most notably in InSnO_x-decorated PtCo catalysts.