Synergistic WS ₂ /NiS Nano‐Micro Heterointerface as Universal pH Electrocatalyst for Efficient Hydrogen Evolution

ABSTRACT Transition metal compound heterointerfaces are promising electrocatalysts for the hydrogen evolution reaction (HER) due to their exceptional electrocatalytic activity arising from their unique electronic band structures, distinctive morphologies, and abundant active edge sites. Herein, a free‐standing WS ₂ /NiS nano‐micro heterointerface grown on nickel foam by a single‐step hydrothermal method is reported. The developed electrocatalyst exhibits HER activity in both acidic and alkaline electrolytes, with overpotentials of 62 and 87 mV at 10 mA cm ^{− 2} , and Tafel slopes of 70 and 71 mV dec ^{− 1} , respectively. This superior electrocatalytic performance is primarily attributed to the high density of exposed unsaturated active edge sites of the WS ₂ nanostructure, which are electrically supported by conductive electron‐transport microchannels of NiS grown on a three‐dimensional conductive nickel substrate. This microstructure not only provides a high aspect ratio but also reduces the aerophilicity of the electrode, thereby enhancing its overall catalytic activity. Furthermore, the electrode can sustain commercially relevant high current densities in the range of 50–100 mA cm ^{− 2} without a substantial deformation or degradation. Density functional theory (DFT) calculations reveal an electronic structure modulation and charge redistribution at the NiS/WS ₂ heterointerface, promoting a synergistic mechanism responsible for the improved HER kinetics.