Preparation And Photocatalytic Properties Of Zn_xCd_1-xS-based Photocatalytic Materials

The excessive use of fossil fuels has caused serious environmental pollution and energy crisis.In order to solve these problems,researchers have been committed to finding a new technology for green and sustainable development.Photocatalysis technology has attracted wide attention due to it has the advantages of high efficiency and environmental friendliness,and shows great potential in wastewater and air treatment as well as energy conversion.The key of photocatalytic technology is semiconductor catalysts.Traditional semiconductor catalysts,such as Ti O₂,Zn O and Zn S have abundant raw materials and low synthesis costs.However,these semiconductor photocatalysts show very low photocatalytic efficiency due to their wide band gaps and thus the low absorption efficiency of visible light.Therefore,the design and preparation of photocatalysts with high catalytic activity and driven by visible light has become an important research topic in the field of material chemistry.Cadmium zinc sulfide(Zn_xCd_1-xS)is a solid solution of zinc sulfide and cadmium sulfide.It has adjustable band gap width as well as good optical and electrical properties.Therefore,Zn_xCd_1-xS has great application potential in photocatalysis.However,its photocatalytic activity was seriously suppressed due to its fast photogenerated carrier recombination rate and the low solar energy utilization.It is reported that the construction of heterojunction is a promising technique to improve the photocatalytic activity.In order to solve the above defects and improve its photocatalytic performance of Zn_xCd_1-xS,a series of Zn_xCd_1-xS based heterojunction photocatalysts with high photocatalytic activity were synthesized by different preparation methods in this thesis.The main contents of the thesis are as follows:（1）Mo S₂/Zn_0.5Cd_0.5S/g-C₃N₄ ternary heterojunction photocatalysts were synthesized via step by step synthesis method.The form of heterojunction can effectively facilitate the separation and transfer of photogenerated charge carriers,and significantly improve the photocatalytic activity and stability of Zn_0.5Cd_0.5S.（2）Zn_0.5Cd_0.5S nanoparticles and snowflake-like Cu₂S were prepared by solvothermal method,and Cu₂S/Zn_0.5Cd_0.5S composite photocatalysts were synthesized by calcination method.Zn_0.5Cd_0.5S nanoparticles were dispersed on the surface of Cu₂S,which improved the dispersion of Zn_0.5Cd_0.5S.In addition,p-n heterojunction was constructed by coupling Zn_0.5Cd_0.5S and Cu₂S,which promoted the separation of photogenerated electrons and holes,leading to improved photocatalytic hydrogen production efficiency.（3）Zn_0.1Cd_0.9S nanorods and Fe WO₄ nanosheets were prepared by hydrothermal method,and one-dimensional Zn_0.1Cd_0.9S/Fe WO₄ nanorods composites were prepared by simple calcination method.Zn_0.1Cd_0.9S/Fe WO₄ composite materials show a wider visible light absorption range due to coupling the narrow energy gap of Fe WO₄,which favors the enhanced utilization of visible light.In addition,the one-dimensional nanorods structure can accelerate the transfer of charge and inhibit the recombination of photogenerated charge carriers,leading to improved photocatalytic performance.（4）Zn_0.1Cd_0.9S/Sn In₄S₈ core-shell heterojunction photocatalytic materials were prepared by hydrothermal method.Sn In₄S₈ coated Zn_0.1Cd_0.9S nanorods to form a special core-shell structure,which is beneficial to the absorption of visible light and the transfer of charge carrier.In addition,the form of heterojunction can promote the separation and transfer of photogenerated electrons and holes,leading to improved photocatalytic activity.