Inhibiting Overoxidation of Dynamically Evolved RuO₂ to Achieve a Win–Win in Activity–Stability for Acidic Water Electrolysis

Proton exchange membrane (PEM) water electrolysis offers an efficient route to large-scale green hydrogen production, in which the RuO₂ catalyst exhibits superior activity but limited stability. Unveiling the atomic-scale structural evolution during operando reaction conditions is critical but remains a grand challenge for enhancing the durability of the RuO₂ catalyst in the acidic oxygen evolution reaction (a-OER). This study proposes an adaptive machine learning workflow to elucidate the potential-dependent state-to-state global evolution of the RuO₂(110) surface within a complex composition and configuration space, revealing the correlation between structural patterns and stability. We identify the active state with distorted RuO₅ units that self-evolve at low potential, which exhibits minor Ru dissolution and an activity self-promotion phenomenon. However, this state exhibits a low potential resistance capacity (PRC) and evolves into inert RuO₄ units at elevated potential. To enhance PRC and mitigate the overevolution of the active state, we explore the metal doping engineering and uncover an inverse volcano-type doping rule: the doped metal-oxygen bond strength should significantly differ from the Ru-O bond. This rule provides a theoretical framework for designing stable RuO₂-based catalysts and clarifies current discrepancies regarding the roles of different metals in stabilizing RuO₂. Applying this rule, we predict and confirm experimentally that Na can effectively stabilize RuO₂ in its active state. The synthesized Na-RuO₂ operates in a-OER for over 1800 h without any degradation and enables long-term durability in PEM electrolysis. This work enhances our understanding of the operando structural evolution of RuO₂ and aids in designing durable catalysts for a-OER.