RuO 2 ‐Based Electrocatalysts for Acidic Oxygen Evolution: Mechanistic Origins of the Activity–Stability Trade‐Off and Pathways to Rational Design

ABSTRACT Ruthenium dioxide (RuO 2 ) is widely considered as a leading non‐iridium candidate for the acidic oxygen evolution reaction (OER) in proton exchange membrane water electrolysis (PEMWE), owing to its high intrinsic activity and comparatively low cost. Its practical implementation, however, is fundamentally limited by a persistent activity–stability trade‐off arising from the close coupling between oxygen evolution, lattice oxidation, and Ru dissolution under strongly acidic and oxidizing conditions. This review summarizes recent progress in RuO 2 ‐based acidic OER catalysts from a mechanism‐centered perspective, with emphasis on how electronic structure, defect chemistry, lattice oxygen reactivity, and spin‐related effects collectively govern catalytic activity, reaction pathways, and degradation behavior. We further discuss how operando characterization has advanced understanding of dynamic active states and stability limits and highlight the emerging role of high‐throughput computation, machine learning, and active learning in accelerating catalyst discovery. By integrating mechanistic understanding, materials engineering, and data‐driven design, this review aims to outline a coherent framework for the development of highly active, durable, and scalable RuO 2 ‐based catalysts for acidic water oxidation.