Synergistic sulfur vacancy engineering and intermetallic Ni₄Mo alloy boosting photocatalytic hydrogen evolution

Photocatalytic hydrogen evolution (PHE) from water splitting represents a promising route for sustainable energy conversion, yet its efficiency is severely constrained by rapid charge carrier recombination and the sluggish surface reaction kinetics of semiconductor photocatalysts. Herein, a synergistic strategy integrating sulfur vacancy (V_S) engineering and intermetallic Ni₄Mo alloy modification is developed to construct a Ni₄Mo/MnCdS (MCS) heterojunction for enhanced PHE. In situ generated V_S serve as anchoring sites for Ni₄Mo growth, enabling strong interfacial coupling. The optimal Ni₄Mo/MCS-V_S catalyst features an exceptional H₂ evolution rate of 30.1 mmol g^-1 h^-1 under visible light-6.3-fold and 5.2-fold higher than pristine MCS and MCS-V_S, respectively. Experimental and DFT studies reveal that V_S/Ni₄Mo synergy optimizes the d-band center, establishes an internal electric field for directional charge transfer, and modulates H* adsorption thermodynamics, collectively suppressing carrier recombination and accelerating water reduction kinetics. This work provides a rational design paradigm for high-performance chalcogenide-based photocatalysts via defect engineering and alloy modification.