Mechanism‐Driven Atomic‐Level Engineering Over RuO 2 ‐Based Catalysts for Proton Exchange Membrane Water Electrolysis

ABSTRACT Proton Exchange Membrane Water Electrolysis (PEMWE) device with merits of high energy efficiency, rapid response, and operational flexibility represents one of the most promising technologies for green hydrogen production. However, the overall hydrogen production efficiency in PEMWEs is frequently constrained by kinetic limitations of the anodic oxygen evolution reaction (OER), due to intricate multi‐step proton‐electron transfer processes. RuO 2 ‐based catalysts remain limited stability, primarily due to intrinsic Ru site overoxidation and lattice oxygen loss during operation, which motivates intensive study into their understanding and mitigating these inactivation mechanisms. Different from traditional surface scale optimization, recent advances in RuO 2 catalyst have focused on mechanism‐driven atomic‐level engineering modification of both Ru sites and coordination environment to simultaneously enhance catalytic activity and stability. However, a comprehensive understanding that bridges the mechanistic complexity of OER with targeted atomic‐scale intervention remains elusive, in response, this review provides a comprehensive overview of recent advances in RuO 2 ‐based nanocatalysts, with an emphasis on OER mechanisms, advanced in‐situ/operando characterizations in PEMWE, and mechanism‐based strategies for regulating stability at the atomic scale. Ultimately, this review concludes by delineating the primary challenges and outlining promising future research directions essential for advancing the practical application of RuO 2 catalysts in PEMWEs.