Stepped Disconnection‐Contributing AgRuIr Nanocrystals with Turtle Shell‐Shaped Oxide Layer for Acidic Water Oxidation

Abstract Stepped disconnections enable innovative catalyst design by breaking spatial symmetry, tailoring electronic bands, and creating localized chemical environments for synergistic water oxidation catalysis. We developed ultrafine AgRuIr nanocrystals with dense stepped disconnections through rapid non‐equilibrium crystallization using medium‐temperature alcohol‐assisted thermal reduction. Large‐sized Ag atoms preferentially located at the line defects between the nanocrystalline domains divided by the stepped disconnection‐mediated grain boundaries. The atomic Ag‐stabilized stepped disconnections across nanocrystalline domains create turtle shell‐shaped oxide layer with abnormal twisted strips, which remarkably enhance H 2 O adsorption and activation kinetics. The catalyst demonstrates exceptional acidic water oxidation performance with an ultra‐low overpotential of 188 mV@10 mA cm −2 and a record‐low 1.82 V electrolysis voltage at 3.0 A cm −2 in AgRuIr∥Pt/C modules, achieving 42.81 kWh/kg H2 efficiency meeting DOE 2026 targets. Enhanced activity originates from abnormal H 2 O aggregation/activation along twisted strips containing disrupted oxygen/metal atoms at Ag‐rich defect lines. Crucially, Ag‐pinned stepped dislocations beneath the active oxide layer inhibit Ru/Ir leaching by elevating lattice diffusion barriers, ensuring operational stability. This work establishes a paradigm for designing next‐generation proton exchange membrane water electrolysis catalysts through engineered stepped disconnection architectures that simultaneously optimize activity and durability.