Recent advances in OER electrocatalysts for PEMWE: From noble-metal efficiency to non-noble alternatives

Proton exchange membrane water electrolysis (PEMWE) is a key technology for sustainable hydrogen production; however, the sluggish oxygen evolution reaction (OER) in highly corrosive acidic environments acts as a major hurdle on commercialization. This review systematically examines recent research trends in OER electrocatalysts, covering both noble and non-noble metal-based materials. For noble metal catalysts, we analyze compositional and structural design strategies—including atomic structuring, strong oxide-support interactions, and high-entropy alloying—to minimize content while maximizing mass activity and long-term stability. Additionally, new classes of non-noble metal catalysts exhibiting stability in acidic environments are explored, with a particular emphasis on spinel oxides, high-entropy chalcogenides, and Mn-based materials. Mechanistic discussions on the adsorbate evolution, lattice oxygen, and oxide path mechanisms are incorporated throughout. Finally, we highlight future research directions, including machine learning-accelerated catalyst discovery and the translation of laboratory-scale performance metrics to industrially relevant membrane electrode assembly conditions.