Phase‐Engineered Bi‐RuO ₂ Single‐Atom Alloy Oxide Boosting Oxygen Evolution Electrocatalysis in Proton Exchange Membrane Water Electrolyzer

Engineering nanomaterials at single-atomic sites can enable unprecedented catalytic properties for broad applications, yet it remains challenging to do so on RuO₂-based electrocatalysts for proton exchange membrane water electrolyzer (PEMWE). Herein, the rational design and construction of Bi-RuO₂ single-atom alloy oxide (SAAO) are presented to boost acidic oxygen evolution reaction (OER), via phase engineering a novel hexagonal close packed (hcp) RuBi single-atom alloy. This Bi-RuO₂ SAAO electrocatalyst exhibits a low overpotential of 192 mV and superb stability over 650 h at 10 mA cm⁻², enabling a practical PEMWE that needs only 1.59 V to reach 1.0 A cm⁻² under industrial conditions. Operando differential electrochemical mass spectroscopy analysis, coupled with density functional theory studies, confirmed the adsorbate-evolving mechanism on Bi-RuO₂ SAAO and that the incorporation of Bi₁ improves the activity by electronic density optimization and the stability by hindering surface Ru demetallation. This work not only introduces a new strategy to fabricate high-performance electrocatalysts at atomic-level, but also demonstrates their potential use in industrial electrolyzers.