Confined Subnanometer Amorphous RuIrO <i> _x </i> Overlayers on Ultrafine Pt Nanowires Achieve Ampere‐Level Durable PEM Water Electrolysis

Abstract Amorphous surfaces, which offer greater tunability compared to their crystalline counterparts, are increasingly recognized as highly active yet unstable phases for specific electrocatalysis reactions under harsh conditions. Whereas successfully creating and stabilizing amorphous surfaces on low‐dimensional electrocatalysts remains a significant challenge. This work elaborately synthesizes ultrathin crystalline/amorphous Pt@RuIrO x core–shell nanowires that effectively overcome the trade‐off among activity, stability, and cost for acidic oxygen evolution reaction (OER) catalysts in proton exchange membrane (PEM) water electrolysis. An in situ oxidation process actualizes the confinement of subnanometer amorphous Ir‐doped RuO x overlayers on ultrathin Pt nanowires. Heteroatom Ir‐doping induces amorphization of host RuO x and effectively modulates the electronic structure and Ru─O covalency. The Pt@RuIrO x nanowires exhibit a substantially intensified robustness when serving as OER active electrocatalysts, demonstrating an ultralow overpotential (146 mV) at 10 mA cm −2 and a remarkable stability. In a practical PEM water electrolyzer, the catalyst requires only 1.55 V cell voltage at 1.0 A cm −2 and maintains long‐lasting operation for over 2000 h. Mechanistic studies validate that the flexible amorphous surface vitalizes the coexistence of multiple reaction pathways, along with an unprecedented lattice oxygen self‐healing capability. These findings establish surface amorphous phase engineering as a powerful strategy for designing high‐performance electrocatalysts.