Study On Photocatalytic Hydrogen Production Of ZnIn₂S₄ Matrix Composites And Its Coupled Oxidation Of Furfuryl Alcohol To Synthesize Furfural

The conversion of light energy into hydrogen（H₂）through semiconductor photocatalysis is one of the most important ways to solve global energy shortages and environmental problems.By combining semiconductor photocatalytic hydrogen generation with organic oxidation reactions,the use of sacrificial agents can be effectively avoided and high value-added chemicals can be coupled with hydrogen production,which is of great research importance.Amongst many semiconductors,metal sulfides exhibit excellent light absorption properties due to their narrower band gap（Eg）than conventional semiconductors,which has led to their widespread attention.This thesis takes ZnIn₂S₄,a typical representative of metal sulfides,as the object of study.While giving full play to the advantages of ZnIn₂S₄,the material is modified by metal ion modification,constructing heterojunction nanocages and constructing heterojunctions to improve the photocatalytic performance of ZnIn₂S₄,given its lack of catalytic active center and the disadvantages of easy compounding of photogenerated electron-hole pairs.The main research of this thesis is divided into three parts as follows:（1）ZnIn₂S₄（ZIS）photocatalyst was synthesized by hydrothermal method,modified by metal ions,and the photocatalytic reaction was carried out with furfuryl alcohol as reaction substrate.The results show that the best hydrogen production performance is the catalyst with metal ion Ni²⁺,and the hydrogen production rate of the sample named 3%-Ni-ZIS can reach 263.527μmol·g^-1·h^-1,which is 11.6 times that of pure ZnIn₂S₄,and the oxidation of furfural alcohol to furfural can be detected by HPLC.The mechanism of improving the photocatalytic performance of 3%-Ni-ZIS was also studied utilizing photoelectrochemical characterization.The results confirmed that Ni²⁺as the capturing center can separate hole electron pairs and promote the generation of more active sites.The hydrogen production rates of furfuryl alcohol,lactic acid,triethanolamine,and benzyl alcohol were further compared.The results show that the hydrogen production rate of furfuryl alcohol is basically the same as that of the conventional sacrificial agent,while benzyl alcohol produces almost no hydrogen,which is attributed to the fact that benzyl alcohol is insoluble in water.（2）ZIF-8 added with different ratios of Ni²⁺was used as a template to generate ZnS hollow nanostructures,and ZnIn₂S₄（ZIS）was grown on its surface to synthesize ZnS@ZIS heterojunction nanocages,which were photocatalyzed with furfuryl alcohol as the reaction substrate.The experimental results showed that the highest hydrogen production rate of 20%-12Ni-ZnS@ZIS reached r（H₂）=292.282μmol·g^-1·h^-1,which was about 13.2 times that of pure ZnIn₂S₄,and the oxidation of furfuryl alcohol to furfural could be detected.The mechanism of the enhanced photocatalytic performance of the synthesized catalysts was investigated by photoelectrochemical and other characterization means,and the results show that growing ZnIn₂S₄ on the ZnS hollow structure is conducive to shortening the charge diffusion path,further promoting the separation of photogenerated electron-hole pairs and greatly improving the photocatalytic efficiency.（3）A constructive heterojunction was used to enhance the photocatalytic activity of ZnIn₂S₄（ZIS）.ZnIn₂S₄ was synthesized by hydrothermal method,and the photocatalytic reaction of ReS₂-ZnIn₂S₄ heterojunctions was carried out by varying the addition of ReS₂ and using furfuryl alcohol as the reaction substrate.The experimental results showed that the highest hydrogen production efficiency of 10%-ReS₂-ZIS could reach r（H₂）=586.445μmol·g^-1·h^-1,which was 23 times that of pure ZnIn₂S₄,and the oxidation of furfuryl alcohol to furfural could be detected.The results show that the construction of ReS₂-ZnIn₂S₄ heterojunction can effectively improve the separation efficiency of photogenerated carriers and also further broaden the light absorption range,which greatly improves the photocatalytic activity.