In-situ synthesis of nickel/palladium bimetal/ZnIn2S4 Schottky heterojunction for efficient photocatalytic hydrogen evolution

Coupling with bimetallic nanoparticles (NPs) has been considered as a promising strategy to enhance photocatalytic hydrogen evolution (PHE) efficiency of semiconductor photocatalysts and simultaneously minimize the use of expensive noble metals. Herein, we firstly synthesized spherical-like ZnIn2S4 (ZIS) by a solvothermal method, and then combined with nickel/palladium (denoted as NiPd) bimetallic NPs to form NiPd bimetal/ZIS Schottky heterojunction. The chemical states of NiPd NPs were confirmed in the form of NiPd bimetal rather than Ni-Pd alloy. The detailed characterization results demonstrated that the deposition of NiPd bimetal played a major role in increasing light harvesting capacity, accelerating charge carrier (electrons and holes) separation and facilitating photogenerated electrons transfer, leading to the boosted PHE performance in NiPd-ZIS photocatalysts. By adjusting Ni:Pd molar ratio in NixPdy-ZIS photocatalysts, the desired sample of Ni3Pd7-ZIS exhibited the highest PHE efficiency (106.6 µmol/h) and apparent quantum yield (AQY) value of 40.22% at 400 nm under visible light as compared to ZIS, Ni-ZIS and Pd-ZIS. The multiple techniques were performed to deeply investigate the photogenerated charge carrier separation, transfer and recombination. The possible mechanism over Ni3Pd7-ZIS sample for boosting PHE performance was presented based on characterization results. On the whole, this work would provide some insights into the development of cost-effective and high-efficiency bimetallic cocatalyst-based photocatalysts.