Directional Hydroxyl Spillover Enhances the Electrocatalytic Performance of Nickel Tungsten Zinc Heterostructure Toward Overall Water Splitting

ABSTRACT In alkaline overall water splitting, excessive hydroxyl adsorption can easily cover active sites for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), becoming a major bottleneck to performance improvement. Herein, a porous bifunctional NiZn/Ni‐Ni 17 W 3 heterostructure is constructed on stainless steel mesh via electrodeposition followed by electrochemical dealloying. Benefiting from the porous morphology after dealloying, electronic redistribution, and directional hydroxyl spillover at the heterointerfaces, NiZn and Ni‐Ni 17 W 3 serve as the dominant active centers for HER and OER, respectively, synergistically optimizing the reaction energy barriers of both processes. The electrode exhibits a HER overpotential of 45 mV (Tafel slope of 82.3 mV dec −1 ) at 10 mA cm −2 and an OER overpotential of 309 mV (Tafel slope of 48.9 mV dec −1 ) at 100 mA cm −2 . It can stably operate at 1.87 V@500 mA cm −2 for 186 h in an anion exchange membrane electrolyzer, providing an effective method for designing high‐performance Ni‐based bifunctional electrocatalysts.