Modulating the Structure of Interfacial Water via Oxygen‐Coordinated Tungsten Single‐Atom on Nickel Sulfide Slab to Boost Alkaline Hydrogen Evolution

Abstract The sluggish kinetics of the Volmer step (water dissociation) in alkaline hydrogen evolution reaction (HER) remain a critical bottleneck. Herein, an oxygen‐coordinated tungsten single‐atom anchored on nickel sulfide (W 1 O/NiS) slabs is proposed to dynamically modulate the interfacial water network. Combining experimental and theoretical approaches, it is revealed that the atomic‐level W 1 O motifs induce a localized electric field, which affords an enriched supply of free water at the inner Helmholtz plane (IHP), as well as reorients interfacial water molecules to a “H‐down” configuration. This structural transition lowers the energy barrier of the Volmer step (H 2 O + e − → H * + OH − ) from 2.41 to 1.02 eV, thereby enhancing the alkaline HER activity. As a result, the developed W 1 O/NiS catalyst achieves an ultralow overpotential of 76 and 236 mV at 10 and 1000 mA cm −2 in 1 m KOH, respectively, maintaining 98% stability after 300 h at a current density of 200 mA cm −2 , surpassing most of the reported Ni‐based HER catalysts. This work provides atomic‐level insights into the electrocatalytic microenvironment engineering for water electrolysis.