Preparation And Photocatalytic Properties Of Titanium Based Composite Microspheres With Hierarchical Structure

As a typical wide band gap metal oxide semiconductor,TiO2 has become one of the research focuses in recent years because of its high catalytic activity,good thermal stability,corrosion resistance to light,environment-friendly and low cost.However,the low utilization of sunlight,the high recombination rate of photo-induced electron-hole pairs formed in photocatalytic processes and the difficulty of recycling restrict its practical application in photocatalysis.In order to improve their catalytic performance,the most commonly used method is heterojunction modification.the preparation and catalytic properties of 3D hierarchical TiO2 microspheres heterojunction composite were investigated in this thesis.The main researches are as follows:We reported in this thesis 3D hierarchical TiO2 microspheres were successfully prepared by solvothermal method.Subsequently,hierarchical Ag2O/TiO2 composite photocatalysts were prepared by chemical deposition in order to improve the photocatalytic activity of TiO2 microspheres.XRD,SEM,TEM,XPS,N2 adsorption and UV-vis were used to characterize the microstructure,element composition and optical absorption characteristics of Ag2O/TiO2 composite photocatalyst.Compared with the pure TiO2,Ag2O/TiO2 composite photocatalyst showed good adsorption performance and high visible light catalytic activity for rhodamine B(RhB).Under the visible light irradiation for 60 min,the removal rate of RhB by Ag2O/TiO2 composite microspheres was 97.3%.We reported in this thesis visible light responsive semiconducting BiOI/TiO2 composite microspheres were prepared by loading BiOI nanoparticles with narrow band gap on the surface of 3D hierarchical TiO2 microspheres via chemical deposition method and characterized.BiOI/TiO2 composite photocatalyst also showed good adsorption performance and high photocatalytic activity for RhB.The removal rate of BiOI/TiO2 composite microsphere for RhB was 95.7%after 60 min irradiation under visible light.We reported in this thesis the hierarchical α-Fe2O3/TiO2 composite photocatalyst were prepared by the twice solvothermal process.The structure and properties of the composite photocatalyst were characterized by various characterization methods,and the photocatalytic degradation activity of the composite photocatalyst was investigated.The photocatalytic activity of the composite microspheres was significantly higher than that of pure TiO2,and the removal rate of RhB was 94.3%after 60 min irradiation in visible lightIt can be concluded that the 3D hierarchical Ag2O/TiO2,BiOI/TiO2,and α-Fe2O3/TiO2 composite microspheres have excellent visible photocatalytic activity,and show good adsorption and high photocatalytic activity for RhB.Among them,Ag2O/TiO2 microspheres have the best catalytic ability.The main reasons may be:① the internal connected pore structure of the hierarchical microsphere can not only improve the absorption and utilization of the incident light on the catalyst surface,but also facilitate the immersion and diffusion of the organic solution;② Ag2O/TiO2 The effect of p-n junction heterostructure on the separation of photogenerated electron hole pairs effectively reduces the recombination probability of photogenerated carriers.The efficiently separation of Ag2O/TiO2 p-n heterostructure on the photogenerated electron hole pairs reduces the recombination of photogenerated charges.This study would provide a facile and feasible strategy to fabricate visible light driven nano-catalyst which could be applied in the fields of waste water treatment,air purification,sensors and solar energy utilization.