Systematic insights into NiMoO4@NiX/MoX (X = S, Se, Te) heterojunction nanoarrays for alkaline hydrogen evolution.

Developing efficient and stable non-precious metal electrocatalysts capable of accelerating the alkaline hydrogen evolution reaction (HER) is crucial for sustainable hydrogen production. Herein, self-supported NiMoO4@NiX/MoX (X = S, Se, Te) heterostructured nanoarrays were fabricated on nickel foam (NF) via a two-step hydrothermal method. Systematic investigations reveal that the introduction of chalcogenides effectively modulates the electronic structure and the oxygen vacancy (Ov) concentration of the catalysts. Notably, the NiMoO4@NiTe2/MoTe2 heterostructure delivered the highest Ov concentration and Mo4+ active site density, driven by the low electronegativity and large atomic radius of tellurium (Te) atoms. Density functional theory (DFT) calculations reveal that chalcogen regulation shifts the d-band center, thereby optimizing hydrogen adsorption, with Te exhibiting the most favorable adsorption behavior for enhanced HER activity. Consequently, the NiMoO4@NiTe2/MoTe2 catalyst required an overpotential of only 46 mV to achieve a current density of 10 mA cm-2 with a Tafel slope of 58.03 mV dec-1, while maintaining stable operation for 70 h. The structure-activity relationships of chalcogenide heterostructures for alkaline hydrogen evolution are revealed in this work.