Preparation And Properties Of P-n Heterojunction Photocatalytic Materials Based On WSe₂

Two-dimensional transition metal tungsten selenide（WSe₂）has good physicochemical stability and wide visible light response range.It shows good potential applications in the field of photocatalysis.However,the fast recombination of electron and hole pairs in WSe₂affects its photocatalytic performance,while the composite p-n heterojunction inhibits the recombination of electron and hole pairs due to the effect of internal electric field.Therefore,three p-n heterojunction composite photocatalytic materials were constructed by compounding WSe₂ with In₂S₃,Bi VO₄,and In₂S₃/Zn In₂S₄ respectively.Under the irradiation of visible light,the synthesized photocatalyst was used to degrade dyes and antibiotics in order to investigate its photocatalytic performance.The photocatalytic reaction mechanism and photogenerated charge transfer path of p-n heterojunction composites were simultaneously discussed by capture test.The main research contents and results of this thesis are as follows:The WSe₂/In₂S₃ p-n heterojunction photocatalyst with good photocatalytic activity and stability was prepared by hydrothermal method.The structure and morphological characteristics of WSe₂/In₂S₃ were analyzed by scanning electron microscope and transmission electron microscope.The degradation experiment of methylene blue（MB）under simulated sunlight revealed that the photocatalytic performance of WSe₂/In₂S₃ was significantly improved,and the degradation rate of MB by WSe₂/In₂S₃（1:10）was the best（92%）.The intermediate products of photocatalytic degradation of MB were detected by liquid chromatography/mass spectrometry.The construction of p-n heterojunction can effectively separate the photogenerated electron hole pairs of WSe₂/In₂S₃ so as to improve its photocatalytic performance.The WSe₂/Bi VO₄ p-n heterojunction photocatalyst was synthesized by hydrothermal solvent method.Under visible light irradiation,10%WSe₂/Bi VO₄ had the best degradation effect on MB,up to 94.5%.After eight regeneration cycles,the degradation rate of WSe₂/Bi VO₄still reached 72%,and showed good photocatalytic stability.Capture experiments and ESR showed that·O₂^-played a major role in the photocatalytic degradation process,followed by h⁺.The excellent photocatalytic performance of WSe₂/Bi VO₄ is attributed to the composition of the internal electric field between WSe₂ and Bi VO₄,which inhibits the recombination of electrons and holes and promotes the migration and recombination of photogenerated carriers.The p-n-p type WSe₂/In₂S₃/Zn In₂S₄（WIZ）heterojunction composite photocatalyst was prepared by simple solvothermal method.MB,tetracycline（TC）,ciprofloxacin（CIP）and 2-chlorophenol（2-CP）were used as target pollutants for visible light photocatalytic degradation to evaluate the photocatalytic activity of WIZ composites.Among them,0.5:8:1.5 WSe₂/In₂S₃/Zn In₂S₄ composite photocatalyst showed the best photocatalytic performance in the degradation of broad-spectrum pollutants,and the removal rates of MB,TC,CIP and 2-CP reached 97%,52.5%,50.5%and 82.1%,respectively.This study shows that the three kinds of composite photocatalytic materials based on WSe₂ p-n heterojunction can effectively accelerate the separation of photogenerated carriers and inhibit the recombination of electron and hole pairs,so as to significantly improve the photocatalytic performance of the composites.Among them,WSe₂/In₂S₃/Zn In₂S₄ with p-n-p heterojunction has the best photocatalytic performance.