Study On The Controllable Synthesis Of ZnIn₂S₄-based Composites And The Performance Of Photolysis Of Water To Hydroge

Indium zinc sulfide（ZnIn₂S₄）is a typical ternary metal sulfur-based photocatalyst with excellent photocatalytic hydrogen production performance.Because ZnIn₂S₄ has a wide range of raw materials,simple chemical composition,relatively easy synthesis,and ZnIn₂S₄ exhibits considerable chemical stability during photocatalysis,as well as low cost,low toxicity and ease of preparation,which has attracted widespread attention.However,the ZnIn₂S₄-based material has problems such as fast recombination of photogenerated electrons and holes,poor carrier migration ability,and structural defects,which limits the photocatalytic performance of ZnIn₂S₄.In order to overcome these shortcomings,this thesis carried out the research on the controllable synthesis of ZnIn₂S₄ matrix composites and the hydrogen production performance of photolysis water.The first work was to control the synthesis of ZnIn₂S₄ and In（OH）₃ composites by adjusting the ratio of thioacetamide to acetamide.Since the solubility product constants of the respective substances are different,In₂S₃ and ZnS₃ are first precipitated at a relatively slow rate and tend to form a hexagonal ZnIn₂S₄ structure.With the increase of the proportion of acetamide added,the sulfur content in the solution decreases,and the excess In³⁺will precipitate into In（OH）₃ and be loaded on the surface of the layered ZnIn₂S₄,which makes many nanosheets coated on the surface of the microspheres.Core-shell ZnIn₂S₄@In（OH）₃ composite.The close interfacial contact between the ZnIn₂S₄ core and the In（OH）₃ shell further promotes charge separation.ZnIn₂S₄ as a cocatalyst,photocatalytic decomposition of water to H² under visible light irradiation on a wide gap In（OH）₃,and 2088μmol^-1·g^-1 on core-shell ZnIn₂S₄@In（OH）₃ The amount of hydrogen produced.In the ZnIn₂S₄@In（OH）₃ structure,the apparent quantum efficiency is 1.45%,which is nearly 2 times higher than the H² yield of the original ZnIn₂S₄.This work provides a highly efficient hydrogen evolution composite and presents a new approach to the development of highly efficient heterojunction photocatalysts.The second work is to control the synthesis of different proportions of ZnIn₂S₄/MoS₂ composites by adjusting the amount of molybdenum source.By one-step hydrothermal method,ZnIn₂S₄ and MoS₂ are precipitated according to the difference of solubility product constants formed by ZnIn₂S₄ and MoS₂.The MoS₂ nanosheet was uniformly wrapped on the surface of the ZnIn₂S₄ flower sphere to form a core-shell composite.MoS₂ is uniformly distributed as a promoter on the surface of ZnIn₂S₄,increasing the specific surface area of the reaction,increasing the reactive sites,and effectively suppressing the recombination of electrons and holes.Compared with the single ZnIn₂S₄ material,the maximum efficiency of ZnIn₂S₄/MoS₂-0.025 composite is 464μmol·g^-1·h^-1,which is about 3 times that of pure phase ZnIn₂S₄ photocatalyst.The results show that the heterostructure is formed between ZnIn₂S₄ and MoS₂,which delays the recombination of photogenerated electron-hole pairs and makes the surface modification of the material an effective way to improve the photocatalytic hydrogen production activity.