Bismuth Oxide Thin Films And Their Photoelectric Property Study

Bismuth oxide,which is non-toxic,visible light-responsed and abundant,has been considered to be a potential photocatalytic material in the field of photocatalyst.Recently,the research mainly focuses on the study on photocatalyst powder.However,when the powder is used photocatalyst,there are some problem such as easily cohesion,loss of activity,blocked of light penetration,difficult separation and recovery and not suitable for continuous fluid system defect limits,which restrict the application of photocatalyst in the process of degradation in water.These limits can be resolved by prepration of photocatalytic thin film in a reasonable method.By the studying of the photoelectric properities of film,it has a further significance for further study on catalytic mechanism of photocatalyst.For this,the bismuth oxide films are prepared by electrostatic induced layer-by-layer self-assemble method in this paper.The effects of morphology structure,photoelectric properties and photocatalytic activity for process are investigated,and formation mechanism of Bi VO₄ film is pointed out.The relationship of photoelectric propertites and photocatalytic mechanism of thin film is studided.In addition,the thin film photoelectrode is prepared by the photocatalyst.By the electrochemical method,the internal charge and photocatalytic mechanism is studied according to the photoelectric properities.The research contents are summarized as follows:?1?The monoclinic Bi VO₄ thin film was prepared by electrostatic induced layer-by-layer self-assemble method.With the 180 min visible light illumination,the Rhodamine B is degraded 26% by the film when the procure contration and crystallization temperature is 0.01 mol/L and 500 oC,respectively.The highly photocatalytic films have high photoelectrons-holes separation rate and charge transfer efficiency when the films are prepared under these conditions.Bi VO₄ films are formed by adsorbing micelles at different times.At the beginning of reaction,the [Bi?NO₃?₃VO₂]-O-FTO layer is formed on the surface of substrate.?BiOVO₃?[Bi?NO₃?₃VO₂] layer was induced by the [Bi?NO3?3VO₂] layer on the substrate to form an electrically neutral Bi OVO3 gel nucleus in the solution.NH3[?Bi OVO₃?NO₃]?BiVO₃?[Bi?NO₃?₃VO₂] layer was formed by the adsorption of NH³⁺ in the precursor solution,and the Bi VO₄ film was formed after crystallization.?2?BiVO₄/TiO₂ composite thin films were prepared by lectrostatic induced layer-by-layer self-assemble method.The phase structure and surface morphology of the samples are analyzed synthetically,and a series of photoelectric properties are studied.It is found that the composite film had no obvious anode spike and the surface electron recombination rate is low.It is found that the interface structure of Bi VO₄/TiO₂ composite film is similar to that of p-n junction,which is beneficial to the transfer of electrons from BiVO₄ to TiO₂ and the transfer of holes from TiO₂ to BiVO₄.Compared with TiO₂ films and BiVO₄ films,composite films have the highest oxidation capacity and carrier concentration.?3?The CeO₂/Ce_xBi_2-xWO₆ heterojunction photocatalyst are prepared by pin coating and photocatalytic properties are studied.The negative photocurrent is related to the hole formed by the electrode.The presence of heterojunction structures increases the photogenerated electron-hole separation rate and reduces the charge transfer time.The factors that improve the photocatalytic effect are the relaxation of the photo-generated electron-hole recombination process and the charge-separation of the heterojunction structure with substitution of Ce³⁺.?4?The formation of Bi₂WO₆ can be inhibited by ethanol and Er³⁺ in microwave solvent.Calciniation can increase the crystallinity.The Er³⁺ doped Bi_2-xEr_xWO₆ thin film electrode is prepared by spin coating and the photoelectric properties are studied.The thin film has high photoelectron-hole separation rate and high oxidation capacity.Er³⁺ makes the Bi_2-xEr_xWO₆ electrode increase photoelectron recombination rate by 70.93%.In addition,the photoelectric conversion characteristic peaks appear at the wavelengths of 542 nm and 654 nm,indicating that the electrode has an upconversion effect.The large photocurrent is mainly the much defects introduced by Er³⁺ doping and the upconversion.