Preparation And Properties Of ZnIn₂S₄ Catalyst And Its Composite Photocatalyst

Overuse of fossil energy has caused obvious energy shortages and environmental problems,solar energy as a renewable energy can greatly alleviate these problems.However,solar energy also has the disadvantage of low energy density.Photocatalytic hydrogen production technology based on semiconductor materials is an effective and clean utilization of solar energy.ZnIn₂S₄ is a ternary metal chalcogenide semiconductor material with suitable bandgap?2.3-2.5 eV?.It has been proved to have good photocatalytic activity,visible light response,easy synthesis and stability.But it also has other semiconductor problems in photocatalysis,such as exciton recombination,which greatly limits the application of materials.Therefore,taking effective measures to solve these problems is the main research objective of this paper.In this paper,based on ZnIn₂S₄,the optimum synthesis parameters are first selected by hydrothermal synthesis method,and then the optimum mass ratio is obtained by using MoS₂ quantum dots as co-catalyst to construct heterojunction structure.Finally,the influence of electronic medium on the heterojunction structure is explored,and the ternary materials with optimum hydrogen production effect are obtained.Details are as follows:?1?ZnIn₂S₄ was synthesized by one-step hydrothermal method.Different precursors,different hydrothermal time and different hydrothermal temperature were used as experimental parameters to optimize the optimal experimental parameters.The synthesized samples are all hexagonal phase.Among them,ZnIn₂S₄ synthesized with ZnCl₂,InCl₃ and thioacetamide?TAA?as precursors and hydrothermal time maintained at 180?for 2 hours has the most efficient hydrogen production activity,and its hydrogen production rate reaches 885 umol·h^-1·g^-1.?2?MoS₂-QDs/ZnIn₂S₄ heterojunctions was successfully synthesized by two-step method.After loading MoS₂-QDs in hydrothermal synthesis of ZnIn₂S₄,the hydrogen production performance of MoS₂-QDs first increases and then decreases with the increase of the loading mass fraction of MoS₂-QDs.Among them,sample 2MoS₂-QDs/ZnIn₂S₄ has the highest hydrogen production rate,which is 7152 umol·h^-1·g^-1,which is more than 9 times that of pure ZnIn₂S₄,and its quantum efficiency can reache to³6.43%.It has good cyclic stability,and its performance has not obviously decreased after repeated cyclic stability tests.It shows that the doping of molybdenum disulfide can effectively inhibit the recombination of electron-hole pairs.For comparison,the hydrogen production rate of mechanical mixed sample 2M-ZIS is only2150 umol·h^-1·g^-1,which shows that the heterojunction structure has better ability to inhibit electron hole-to-hole recombination.?3?The hydrogen production rate of ZnIn₂S₄ and 2MoS₂-QDs/ZnIn₂S₄ was significantly increased by adding 1wt%electronic medium?rGO and CNTs?in the hydrothermal synthesis process.The hydrogen production efficiency of samples1rGO/2MoS₂/ZnIn₂S₄ and 1CNTs/2MoS₂/ZnIn₂S₄ increased significantly,reaching22994 umol·h^-1·g^-1 and 32676 umol·h^-1·g^-1 respectively,which were 25 and 36 times as much as that of ZnIn₂S₄,and more than 3 and 4 times as much as that of 2MoS₂-QDs/ZnIn₂S₄,respectively.This shows that the addition of electronic media can significantly improve the photocatalytic performance of the original semiconductor materials and further prevent the recombination of photogenerated electrons and hole pairs.