The Transfer Direction Of Photogenerated Electrons In MTiO₃/TiO₂ Composite Semiconductor

With the emergence of global environmental deterioration and energy shortage,modified semiconductor materials have become a hot research field.The purpose of semiconductor modification is to improve the catalytic activity of semiconductor,and different methods need to take different influencing factors into account so as to prepare a modified material with high catalytic activity.Ion doping needs to consider the factor of type,dosage and doping position.The type,energy levels and energy band width of semiconductor need to be considered in semiconductor composites.Dye sensitization needs to consider the type of dye and the compatibility between dye with semiconductor.Understanding the photocatalytic mechanism of different systems can help us design excellent photocatalytic materials.In this paper,the MTiO₃/TiO₂ composite system is taken as the representative to analyze the influence of semiconductor parameters on the properties of composite semiconductors,and to elaborate the photocatalytic mechanism of the semiconductor composite.The research contents are as following:?1?In this paper,the MTiO₃ powder prepared by hydrothermal or sol-gel method was coated on the carrier to form a film by coupling method,and then TiO₂ was supported on the MTiO₃ film by dip-coating method,finally the MTiO₃/TiO₂ film was prepared.Using characterization methods analysis MTiO₃/TiO₂ thin films calcinated under 350 ^oC,we see that low temperature calcination can affect the XRD results of composite membrane,and found that carbon doped in the anatase type of TiO₂ lattice gap.Because of the heterojunction formed between MTiO₃ and carbon-doped TiO₂,the light absorption range and intensity of the composite films have changed,and different titanates have different effects on the energy bandwidth of the composite semiconductor due to their different parameters.?2?The composite films were immersed in silver nitrate solution for 4 h under ultraviolet light,and we can determine the reduction site on the films through EDS surface scanning diagram,and judge the direction of electron flow.The EDS surface scanning element diagram shows that silver is preferentially deposited on the side of the heterojunction:The Ag elements in the EDS of BaTiO₃/TiO₂,NiTiO₃/TiO₂ and PbTiO₃/TiO₂ photocatalyst were distributed on one side of TiO₂,while the silver deposition of TiO₂/CaTiO₃,MgTiO₃/TiO₂and ZnTiO₃/TiO₂ photocatalyst was mainly on the side of titanate.The reduction site was determined by silver deposition because Ag⁺in silver nitrate would have a reduction reaction with electrons and deposit on there.Therefore,according to the characterization results,electrons would eventually migrate to the semiconductor with higher Fermi level.According to the electron flow direction of the semiconductor and their respective energy band parameters,we can define the photocatalytic mechanism in the MTiO₃/TiO₂ composite system.The study shows that the transfer direction of photogenerated electrons in the MTiO₃/TiO₂ composite system conforms to the theory of semiconductor physics.In addition,it afford an idea for the preparation of composite semiconductor materials with high catalytic activity.