pH Modulated Atomic Distribution in NiMo Alloys for Ultrastable Water Electrolysis

ABSTRACT While surface engineering dominates the design of alkaline hydrogen evolution reaction (HER) catalysts, the critical role of subsurface architecture remains largely unexplored due to synthetic challenges. Herein, we present a “precursor hereditary” strategy that modulates the pH‐dependent speciation of molybdate clusters to precisely dictate the migration kinetics of metal atoms during thermal reduction, thereby enabling the formation of a customized depth profile with optimized electronic structure. The resulting compositional gradient significantly downshifts the d‐band center, balancing hydrogen adsorption/desorption energetics. Consequently, the optimized catalyst exhibits an ultralow overpotential of 61 mV at 200 mA cm −2 and outstanding kinetics. Notably, in an anion exchange membrane water electrolyzer (AEMWE), it delivers an industrial‐level current density of 1.5 A cm −2 at 1.88 V and operates stably for 2 500 h with a negligible degradation rate (28 µV h −1 ). This work establishes a universal paradigm for manipulating atomic‐scale depth profiles to bridge the gap between fundamental surface science and practical electrolyzer applications.