Preparation Of Zinc Indium Sulfide Composite Photocatalysts And Study On Its Water Splitting Performance Under Visible Light

As one of the most attractive and eco-friendly technologies,semiconductor photocatalysis is demonstrated as a potential strategy to solve global energy shortage environmental pollution problems.Regarding semiconductor-based photocatalysts,Ternary metal sulfide ZnIn₂S₄ with layered structure has become research hotspots owing to its superior visible light absorption,high chemical durability and low cost.Nevertheless,the photocatalytic activity of pristine ZnIn₂S₄ is unsatisfactory due to the limited range of visible light absorption and fast recombination rate of light-induced electrons and holes.In order to improve the photocatalytic performance of ZnIn₂S₄,the problem of charge carrier migration and separation in ZnIn₂S₄ nanosheets was solved by introducing non-precious metal catalyst,solid-state electronic medium and constructing z-heterojunction.The composite photocatalyst was studied by a series of material characterization and photocatalytic activity evaluation experiments.This work can be divided into the following three parts:（1）2D/2Dβ-Ni S/ZnIn₂S₄ photocatalytic system was constructed by a two-step method for efficient photocatalytic hydrogen production under visible light.The physical and chemical ofβ-Ni S/ZnIn₂S₄ composite were characterized by X-ray diffraction（XRD）,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,and UV–visible diffuse reflectance spectroscopy（DRS）.The results reveal that the prepared composite photocatalyst has good interface contact between the ZnIn₂S₄ nanosheets and cocatalystβ-Ni S nanosheets,which is conducive to the transfer and separation of charges.Under visible light irradiation,3%Ni S/ZIS showed the best hydrogen production rate of 13.43 mmol g^-1 h^-1,which is about 10times that of pure ZnIn₂S₄ nanosheets,and the composite photocatalyst showed excellent photocatalysis stability.Finally,based on the characterization and photocatalytic activity results,a possible charge transfer mechanism was proposed.（2）CoP nanosheets were anchored on the surface of two-dimensional RGO by hydrothermal-assisted phosphating method to synthesize Co P/RGO composite cocatalyst,and then the Co P/RGO/ZnIn₂S₄ photocatalytic system was constructed by a simple mechanical mixing method.The crystal structure,micromorphology,chemical state and light absorption characteristics of Co P/RGO and Co P/RGO/ZnIn₂S₄nanocomposites were studied by X-ray diffraction,scanning electron microscopy,transmission electron microscopy,and UV–visible diffuse reflectance spectroscopy.The photocatalytic performance of the Co P/RGO/ZnIn₂S₄ composite was investigated through the photocatalytic activity evaluation experiment.the 4-CRZ sample showed the best hydrogen production rate of 18.73 mmol g^-1 h^-1,which was nearly 13.8 times higher than that of the pure ZnIn₂S₄ nanosheets.The electron transfer path in the CoP/RGO/ZnIn₂S₄ composite was studied by photoelectrochemical test,and the corresponding photocatalytic reaction mechanism was proposed.（3）Theα-Fe₂O₃/RGO/ZnIn₂S₄ all-solid-state Z-scheme heterojunction photocatalytic system was constructed using RGO nanosheets as the solid electronic medium.The close interfacial contact inα-Fe₂O₃/RGO/ZnIn₂S₄ ensures the effective flow of charge carriers between ZnIn₂S₄ andα-Fe₂O₃,realizing high-efficiency photocatalytic total water splitting.By optimizing the ratio of each component,the 3-FRZ sample photocatalytic overall water splitting H2 and O2 release rates under visible light irradiation were 616μmol·g^-1 h^-1 and 275.3μmol·g^-1 h^-1,which is the ZnIn₂S₄ Andα-Fe₂O₃ 2.3 times and 10 times.In addition,the degradation efficiency of the 3-FRZ sample for BPA under visible light is as high as 97.2%.Through fluorescence test and photoelectrochemical test,the charge transfer path inα-Fe₂O₃/RGO/ZnIn₂S₄ composite was explored,and the corresponding photocatalytic reaction mechanism was proposed.