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.