Dynamic-Cycling\nZinc Sites Promote Ruthenium Oxide\nfor Sub-Ampere Electrochemical Water Oxidation

Although iridium-based electrocatalysts are commonly\nregarded as\nthe sole stable operating acidic oxygen evolution reaction (OER) catalysts\nin proton-exchange membrane water electrolysis (PEMWE) devices, their\nexorbitant cost and scarcity severely restrict their widespread application.\nHerein, we introduce a promising alternative to iridium: zinc-doped\nruthenium dioxide (TE-Zn/RuO<sub>2</sub>), which exhibits remarkable\nand enduring activity for acidic OER. <i>In situ</i> characterizations\nelucidate that the dynamic cycling of zinc dopants serves as both\nelectron acceptors and donors, facilitating the activation of Ru sites\nat low overpotentials while thwarting peroxidation at high overpotentials,\nthus concurrently achieving heightened activity and robust stability.\nAdditionally, the incorporation of zinc induces weakened Ru–O\ncovalency, thereby stabling *OOH intermediates and instigating a sustained\nadsorbate evolution mechanism, dramatically stabilizing the RuO<sub>2</sub> lattice. Importantly, the TE-Zn/RuO<sub>2</sub> catalyst\nas an anode exhibits good stability over 300 h at a water-splitting\ncurrent of 500 mA cm<sup>–2</sup> in the PEMWE device, underscoring\nits considerable promise for practical applications.