Study On MoS₂ Based Composites:preparation And Their Photocatalytic Properties

MoS₂is a layered transition metal sulfide with a band gap ranging from 1.29–1.9 e V.MoS₂nanostructures have large surface area and strong absorptive capacity.There are a large number of unsaturated bonds on the edge of MoS₂nanostructures.Thus,the number of end groups per unit area can be increased significantly,resulting in the increase of the active sites of MoS₂,indicating potential application in photocatalytic field.In this thesis,co-catalytic properties of three MoS₂-based ternary composites catalysts were studied.Novel MoS₂/MoO₃/TiO₂ternary composite catalysts were developed.The photocatalytic performance of the MoS₂/Mo O₃/Ti O₂ternary composites was evaluated by photo-degradation of rhodamine B（Rh B）.It was found that the photocatalytic ability of the composites was strongly dependent on the mass ratio of MoS₂–Mo O₃to MoS₂–Mo O₃–Ti O₂.The ternary composite catalyst with optimum composition showed a fast degradation rate(maximum 0.138 min^-1),which could degrade over 95%of Rh B solution（10 mg/L）within20 min under visible light（λ≥420 nm）irradiation.The possible photocatalytic mechanism was proposed based on the trapping photocatalytic experiment and band alignment of the composite.The synergistic effect of the strong absorption of the catalyst and the efficient separation of photogenerated electron–hole pairs by the novel ternary composite contributed to the enhanced photocatalytic activity.MoS₂/TiO₂/carbon cloth（CC）ternary composite catalysts were prepared by hydrothermal method.The difference of photocatalytic performance of CC/MoS₂/Ti O₂ternary composites prepared by one-step（I）and two-step（II）hydrothermal processes was studied in detail.In comparison,CC/MoS₂/Ti O₂（II）ternary composite showed better crystal quality,and stronger adsorption capacity and photocatalytic ability.The conductive carbon cloth not only helped increasing the contact area with the degraded material,but also made the recycle processes simple and convenient.The main active species in the photodegradation of CC/MoS₂/Ti O₂ternary composite catalyst are·O₂^-and h⁺.CC/MoS₂/Ti O₂ternary composite has a strong adsorption capacity for organic matter,combined with the visible light absorption of the catalyst and the synergistic effect of conductive carbon cloth promotes the effective separation of photogenerated electrons and holes,and improves the photocatalytic performance of the composite.CC/MoS₂/Zn S ternary composite catalysts were grown on carbon cloth by one-step hydrothermal method.The photocatalytic properties of the composites with different Mo/Zn ratios were investigated.It was found that when the Mo/Zn molar ratio was 7:1,the CC/MoS₂/Zn S ternary composite exhibited optimum photocatalytic performance,degrading over 90%Rh B in 90 minutes.The large specific surface area of CC/MoS₂/Zn S ternary composite enhanced its absorption capacity,which improved the photocatalytic activity of the composite.Photogenerated electrons migrates from the conduction band of MoS₂to the conduction band of Zn S,and then to the surface of carbon fiber.Electrons react with O₂to·O₂^-,and holes converted to·OH,which reacted with organic dyes,resulting in the rapid degradation of Rh B.