Research On Synthesis And Photocatalytic Property Of Zn₂S₄-based Photocatalytic Materials

With the rapid development of industrialization,a large number of non-renewable energy sources such as coal,oil,and natural gas have been exploited and used.At the same time,the products of fossil fuels have brought huge environmental problems,such as abnormal weather and frequent natural disasters.Therefore,solving energy shortage and environmental pollution has become an urgent need for our country to implement sustainable development strategies and improve people’s quality of life.Photocatalytic technology can convert low-density solar energy into clean and easy-storable chemical energy,and has great potential in new energy development and environmental purification.Indium zinc sulfide（ZnIn₂S₄）has been introduced into the field of photocatalysis due to its unique energy band structure,ultra-high specific surface area and good hydrothermal stability,and has attracted widespread attention.In this thesis,ZnIn₂S₄ is mainly combined with other semiconductor materials to construct a new and efficient photocatalyst,The specific work content is as follows:（1）Study on the preparation of ZnIn₂S₄/MIL-101（Cr）-NH₂ and its photocatalytic degradation performance of Rh B.First,the granular MIL-101（Cr）-NH₂ is prepared by hydrothermal reaction,and then the MIL-101（Cr）-NH₂ is mixed with the raw materials of ZnIn₂S₄,and the ZnIn₂S₄ nanosheets are uniformly dispersed on the MIL-101（Cr）-NH₂ surface by in suite method.Finally,Rh B was degraded under a 300 W xenon lamp（λ≥420nm）,and the removal rate of the best sample reached 99%within 180min.The photocatalytic mechanism of the system was analyzed in detail through free radical capture experiments.（2）Research on the preparation of ZnIn₂S₄/MIL-88A（Fe）and its photocatalytic hydrogen production performance.First,the hexagonal rod-shaped MIL-88A（Fe）is synthesized by the hydrothermal method,and then the ZnIn₂S₄/MIL-88A（Fe）core-shell structure heterojunction is synthesized by the oil bath method.Finally,lactic acid was used as a sacrificial agent to evaluate the reactivity of the material through photocatalytic hydrogen production.Under visible light irradiation,the hydrogen production rate of the optimal composite sample reaction for 3 h was as high as 8556.4μmol·g^-1·h^-1.After three cycles,the hydrogen production rate did not decrease significantly,indicating that the catalyst has good stability.Finally,the corresponding photocatalytic reaction mechanism is proposed for the composite system.（3）Study on the preparation of MOF-derived iron oxide（Fe₂O₃,Fe₃O₄）and ZnIn₂S₄ composite material and its photocatalytic degradation performance of Rh B.The experiment in this chapter first uses the hexagonal rod-shaped MIL-88A（Fe）as the template.The template is pyrolyzed by different gas atmospheres（nitrogen and air）to obtain different iron oxides,namely magnetite Fe₃O₄ and hematiteα-Fe₂O₃.Then by the oil bath method,the 2D ZnIn₂S₄ nanosheets were grown in situ on the 1D rod-like iron oxide surface to form a 2D/1D core-shell structure.Finally,using Rh B as a simulated pollutant to conduct photocatalytic degradation experiments on the prepared materials,the removal rates of ZnIn₂S₄/Fe₂O₃ and ZnIn₂S₄/Fe₃O₄ on Rh B reached 71.4%and 96.7%within 60 minutes,respectively.For the difference in performance,a detailed explanation is given from the analysis of the photocatalytic mechanism.（4）Research on the preparation of MOF-derived Ni-Fe LDH and ZnIn₂S₄ composite material and its photocatalytic hydrogen production performance.First,using MIL-88A（Fe）as a template,Ni-Fe LDH was prepared by ion exchange.The ZnIn₂S₄ nanosheets were uniformly dispersed on the surface of the rod-shaped layered hollow Ni-Fe LDH by the in-situ growth method to form a core-shell structure.Then the photocatalytic reaction activity of the composite system was studied through the photocatalytic hydrogen production experiment,in which triethanolamine was used as the sacrificial agent.Under visible light,the hydrogen production rate of the ZnIn₂S₄/Ni-Fe LDH composite material is as high as 6107μmol·g^-1·h^-1 within3 h,which is 6.7 times that of pure ZnIn₂S₄(906μmol·g^-1·h^-1).Finally,the reaction mechanism analysis shows that the composite system is a typical type Ⅱ heterojunction.