Breaking the Activity–Stability Trade‐Off of RuO 2 ‐Based Electrocatalysts for Proton Exchange Membrane Water Electrolyzer: Modulation Strategies and Mechanism Elucidation

Proton exchange membrane water electrolyzer (PEMWE) is a pivotal technology for renewable green hydrogen production, yet its large‐scale deployment is limited by expensive and rare Ir‐based oxygen evolution reaction (OER) electrocatalysts. RuO 2 emerges as a promising Ir‐free alternative attributed to relatively high reserves and optimal binding affinity for OER intermediates that overcomes the strong‐binding limitations of Ir‐based catalysts. However, the applications of RuO 2 in PEMWE are severely hindered by the inherent activity–stability trade‐off and severe overoxidation/leaching under harsh industrial operation. Against this background, various advanced electronic and geometric modulation approaches have been adopted to simultaneously enhance the activity and stability of RuO 2 to push forward its practical applications. In this review, we start with a comprehensive overview of the recently developed strategies for enhancing the activity and stability of RuO 2 in PEMWE. Then, the underlying mechanisms of each strategy in breaking the activity–stability trade‐off of RuO 2 ‐based electrocatalysts are systematically described. Finally, key challenges and forward‐looking optimization strategies are proposed. This review will deliver fundamental insights and rational guidelines for designing robust low‐cost RuO 2 ‐based electrocatalysts toward scalable industrial PEMWE deployment.