High‐Entropy Materials for Durable Oxygen Evolution in Acidic Water Electrolysis

ABSTRACT Proton exchange membrane water electrolysis (PEMWE) has emerged as an attractive approach for green hydrogen production. However, its large‐scale commercialization is constrained by the scarcity and high cost of Ir‐based anode catalysts for the oxygen evolution reaction (OER) under acidic conditions. Conventional approaches, including alloying and structural engineering, often suffer from an inherent activity–stability trade‐off in such corrosive acidic media. This review highlights high‐entropy materials (HEMs) as a practical material platform to address the Ir bottleneck in acidic OER. The unique characteristics of HEMs, including high configurational entropy, sluggish diffusion, and severe lattice distortion, enable the structural stabilization of active sites and the effective suppression of metal dissolution. Recent progress can be categorized into two representative development pathways: (i) Ir‐lean strategies, which exploit high‐entropy lattices to maximize atomic utilization and promote self‐passivation, and (ii) Ir‐free strategies, which stabilize Ru or selected nonprecious metals through entropic and electronic (cocktail) effects. Finally, we discuss remaining challenges and future research directions aimed at achieving durable, cost‐effective anodes for large‐scale PEMWE systems.