Doped Ru-Based Catalysts for Proton Exchange Membrane (PEM) Water Electrolysis: Advances in Boosting Activity and Stability for the Acidic Oxygen Evolution

Proton exchange membrane water electrolysis (PEMWE) is a promising technology for green hydrogen production, yet its efficiency is limited by the sluggish kinetics and instability of the oxygen evolution reaction (OER) under acidic conditions. Among various catalysts, Ru-based materials show superior intrinsic activity but suffer from dissolution and structural degradation, highlighting the need for rational design strategies. This review summarizes recent progress in heteroatom doping strategies for Ru-based acidic OER catalysts. The fundamental OER mechanisms, including the adsorbate evolution mechanism (AEM), lattice oxygen-mediated mechanism (LOM), and oxide pathway mechanism (OPM), are briefly outlined to clarify the correlation between reaction pathways and catalyst structures. Then focusing on how doping modifies the electronic configuration and lattice distortion of RuO₂ to optimize reaction pathways and intermediate adsorption. Typical cases of nonmetal, high-valence metal, low-valence metal, and multielement co-doping, are compared in terms of their effects on activity and stability. Finally, challenges and future directions for rational catalyst design are proposed.