Mechanism‐Guided Design Strategies for Stabilizing Ruthenium Oxide Anodes in Proton Exchange Membrane Water Electrolysis

Proton exchange membrane water electrolysis (PEMWE) is a leading route to low‐carbon hydrogen, yet its anodic oxygen evolution reaction (OER) remains constrained by the scarcity and instability of noble‐metal catalysts under strongly acidic, high‐current operation. Ruthenium oxides are attractive alternatives to iridium‐based anodes because of their high intrinsic activity, but they face a fundamental activity–durability trade‐off: kinetic acceleration often coincides with oxygen‐anion redox, vacancy accumulation, overoxidation, and Ru dissolution. This review argues that recent progress in Ru‐based acidic OER catalysts is best understood through a mechanism‐guided framework that links proton management, interfacial water organization, metal–oxygen redox buffering, regulation of oxygen balance, and cooperative O–O coupling. We show that acidic PEM OER is governed not only by adsorption energetics, but also by the coupled evolution of the catalyst–ionomer–water microenvironment and the Ru–O redox manifold. We further discuss how these design levers redistribute competition among the adsorbate evolution mechanism, lattice‐oxygen‐mediated pathways, and dual‐site coupling routes, and how theory and operando methods guide translation from half‐cells to membrane electrode assemblies (MEAs) while establishing mechanism‐aware durability benchmarks.