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.