Abstract: Despite the existence of plentiful photocatalyst heterojunctions, their separation efficiency and charge flow precision remain low on account of lacking interfacial modulation. Herein, through a defect-induced heterojunction constructing strategy, Ni₄Mo alloys were in-situ grown on the unsaturated coordinated sulfur atoms of sulfur vacancies-rich ZCS (Sv-ZCS) via interfacial Ni-S covalent bonds. The experimental and theoretical results reveal that these unsaturated sulfur atoms induced by sulfur vacan-cies vastly facilitate to anchor more Ni-Mo nanoparticles and form abundant Ni-S covalent bonds, mean-while, these sulfur vacancies could form dual internal electric field (IEF) and work with Ni-S covalent bonds as ‘‘Electron Bridge” to further accelerate photoelectrons transfer, as well as promote the activation of water molecules and the desorption of hydrogen proton. Accordingly, the optimized Ni₄Mo/Sv-ZCS composite achieves an improved photocatalytic hydrogen evolution (PHE) rate of 94.69 mmol h^-1 g^-1 without an evident decrease after 6 cycles of photocatalytic tests, which is 21.2 and 1.94 times higher than those of Pt/ZCS and Ni₄Mo/ZCS, respectively. This tactic opens a new way for optimizing Zn_xCd_1-xS-based heterojunctions by constructing sulfur vacancies and covalent bonds as ‘‘Electron Bridge” to enhance the activity of PHE.

Key words: Ni₄Mo, Sulfur vacancies-rich Zn_xCd_1-xS, Electron Bridge, Photocatalytic hydrogen evolution