H* Site‐Blocking Alleviated Through Collaborative Copper Alloying for Large‐Current Hydrogen Production

Abstract Industrial alkaline water splitting requires cost‐effective hydrogen evolution reaction (HER) electrocatalysts that can balance the adsorption of H 2 O, H*, and OH*. Despite robust water adsorption/dissociation and moderate H* adsorption, NiMo alloys are plagued by competitive OH* adsorption, which induces H* site‐blocking, thereby impeding the Volmer step and necessitating large overpotentials. Here, an integrated electrode design is developed by incorporating NiMoCu catalysts onto a stainless‐steel mesh (SSM) through Cu alloying. The optimized NiMoCu achieves a current density of 500 mA cm −2 at only 175 mV overpotential, nearly 19.5 and 6.9 times higher than NiMo and Pt/C, respectively. In situ characterizations and theoretical calculations reveal that segregating H* and OH* adsorption sites (Ni─Cu for H* and Mo for OH*) effectively mitigates H* site‐blocking. This segregation optimizes the short‐range adsorption of various intermediates, thereby enhancing the kinetics from Volmer to Heyrovsky step. Moreover, the regular 3D micrometer‐scale structure of SSM support promotes long‐range mass transfer, further improving the overall performance. When paired with NiFe LDH for anion‐exchange‐membrane (AEM) water splitting, the NiMoCu(−)||NiFe LDH(+) electrolyzer delivers 2 A cm −2 at 1.98 V, with robust durability. This strategy is extendable to NiMoCo and NiMoZn catalysts, offering a universal approach for efficient hydrogen production.