Fabrication of noble-metal-free hierarchical rectangular tubular S-scheme NiS/ZnIn2S4/AgIn(WO4)2 nanocomposite for highly efficient photocatalytic hydrogen evolution

Accelerating the separation and transfer of photoinduced charge carriers is crucial for designing photocatalysts with superior photocatalytic hydrogen evolution (PHE) activity. Herein, a novel rectangular tubular hierarchical NiS/ZnIn2S4/AgIn(WO4)2 heterostructure was established by in-situ growing ZnIn2S4 nanosheets on the surface of tubular AgIn(WO4)2 and NiS nanoparticles (NPs) further deposited as co-catalysts for the first time. Based on the experimental and theoretical calculation results, the fabrication of ZnIn2S4/AgIn(WO4)2 S-scheme heterojunction as well as NiS NPs as active centers could account for the fast photogenerated charge carriers transfer and enhanced PHE activity. Notably, under simulated sunlight irradiation, the optimal NiS/ZnIn2S4/AgIn(WO4)2 composite exhibited a high PHE rate of 4818 µmol·g−1·h−1 without adding any noble-metal co-catalyst, which was about 24 and 3.7 times higher than that of pure AgIn(WO4)2 and ZnIn2S4, respectively. Meanwhile, the rate was up to 83 % of the value of ZnIn2S4/AgIn(WO4)2 with 3 wt% platinum (Pt) as co-catalyst, which meant that NiS NPs could replace Pt as an efficient noble-metal-free co-catalyst. This work provided a feasible approach to utilize the synergistic effect between co-catalyst and heterojunction for constructing efficient photocatalytic systems, and further confirmed the potential application of AgIn(WO4)2 with the special tubular morphology for PHE reaction.