Multi-vacancy synergistic effect in a NiSe0.4S1.6/ZnO heterostructure for promoting photocatalytic hydrogen production

Defect engineering is one of the methods to improve catalytic activity of photocatalysts, but there are few reports on multi-vacancy systems. In this paper, S doping NiSe2 (NiSe0.4S1.6, NSS) was synthesized and further the NSS/xZnO heterostructures containing Ni, Se and O vacancies were constructed. The hydrogen and active oxygen ions are in situ generated at oxygen vacancy (VO) in ZnO, which greatly reduce the recombination of photocarriers, and the generated active oxygen ions and sacrificial agent anions (S2−, SO32−) involve in the regeneration of oxygen vacancy, which may be one of the reasons for the high activity and stability of the composite catalysts. The polarization electric field is formed by regulating the selenium and nickel double vacancy (VSe, VNi) generated by sulfur doping NiSe2, which further improves the charge separation leading to the promotion of photocatalytic hydrogen production. The synergistic effect of the three types of vacancies and the redox properties of the composite catalyst lead to a high H2 production rate of 17.04 mmol·g−1·h−1, 54 and 76 times higher than NSS and ZnO, and a high apparent quantum yield of 15.30 % at 400 nm. The hydrogen production mechanism was explored by EPR, Mott-Schottky, VB-XPS, in suit XPS, DFT, etc. This work proves that the combination of transition metal oxides with rich oxygen defects and metal chalcogenides with metal and chalcogen di-vacancies containing local polarized electric fields is an effective strategy to design high active photocatalyts for water splitting.