| With the development of technology and economy.the environmental pollution has become a serious threat to the survival of human beings.As a kind of green and clean pollutant degradation technology,semiconductor photocatalysis has a bright future.Titanium dioxide(TiO2)has a rich source,non-toxic and stable characteristics,and has been widely studied and applied as a photocatalyst.However,the wide band gap made TiO2 only response in the ultraviolet band,limiting its practical application.In the past decades,a large number of studies have focused on extending the photocatalystic activity of TiO2 into the visible light band.In these efforts,a viable and effective way is to form heterojunctions between narrow bandgap semiconductors and TiO2.The separation of photo-generated carriers can be promoted by the heterogeneous junctions.The ferroic layered perovskite oxide Bi4Ti3O12 has a band gap of about 3.08 eV and long carrier lifetime,and it is chemically stable.The built-in electric field due to the ferroelectricity may further promote the separation of photogenerated electron-hole pairs,so has a good photocatalytic efficiency in the visible light band.The Ti-O octahedron basic structure of layered perovskite oxide Bi4Ti3O12 is similar to TiO2,which may facilitate the formation of heterogeneous junctions with interface match.At the same time,this similarity also provide the structural basis for synthesizing Bi4Ti3O12/TiO2 heterojunction by using TiO2 as the titanium source.The innovation of this paper is to synthesize Bi4Ti3O12/TiO2 heterojunction by hydrothermal method,and integrate the different semiconductors with different electronic structures to sensitize the wide bandgap photocatalyst with narrow bandgap photocatalyst.By controlling the ratio of the two phases,the photocatalytic performance of the photocatalytic system for both UV and visible light can be enhanced,and as a possible application it can be applied to the treatment of pollutants.The detailed works of this thesis are as follows:Chapter 1:We introduce the basic principle of semiconductor photocatalysis,the status of the application and research,and summarize the shortcomings and problems of photocatalysts which need to be solved.And corresponding methods are also mentioned in the chapter.Based on the above review,the significance of this research of this paper is introduced,and the general framework,the methods of hydrothermal synthesis of Bi4Ti3O12/TiO2 heterojunctions as well as the theoretical foundation of this study are proposed.Chapter 2:The synthesis of Bi4Ti3Oi1/TiO2 heterojunction by hydrothermal method are introduced.The morphology,optical properties,optical and electrical properties and photocatalytic properties of the samples prepared under different two-phase ratios are also investigated.Chapter 3:Bi4Ti3O12/TiO2 heterojunctiones were synthesized by hydrothermal method,with TiO2 as the Ti source and Bi(NO3)3 as the Bi source.This heterogeneous structure can more effectively improve the absorption for visible light and enhance the photodegradation of organic pollutants than TiO2.When the mass ratio of TiO2 and Bi(NO3)3 was 5:2,the best photodegradation performance can be observed under UV and visible light.The photoelectrochemistry test showed that this enhancement not only came from the absorption of visible light band,but also from the enhancement of photogenerated charge separation.Bi4Ti3O12/TiO2 has a good photodegradation ability under visible light irradiation.Chapter 4:the main results of the w orks are summarized,and the future works for this research are suggested. |
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