Preparation And Performance Study Of TiO₂-based Visible Light Photocatalyst

TiO₂-based visible light photocatalysts generally possess good chemical stability,efficient light-responsiveness and various morphologies,structures and compositions,which make them extremly promising in the field of water spliting,photodegradation,photocatalytic CO₂ conversion,water treatment and so on.Most of their applications also widely involve in our daily lives.According to numerous of researches,among different approaches,designing and constructing TiO₂-based composite materials is the most simple and efficient methods for preparing highly efficient visible light photocatalysts.Introducing different metal nanoparticles and semiconductor materials can effectively improve the photocatalysis performances of TiO₂-based materials.This thesis starts from designing and constructing the structures of TiO₂-based composite materials.It aims to explore new strategies for preparing TiO₂-based visible light photocatalysts and attempt to prepare advanced TiO₂-based visible light photocatalysts.Furthermore,the applications of these novel materials in the field of photodegradation and photocatalytic synthesis of fine chemicals are carefully studied.In the chapter ?,we report a novel TiO₂ composite nanofibers embedded with Au and Fe₃O₄ nanoparticles.Combining the electrospinning technology with the impregnation method,we can effectively incorporate the Au and Fe₃O₄ nanoparticles into the TiO₂ composite nanofibers.As-obtained composite materials show uniform morphologies and particle sizes,excellent visible light-responsiveness and good magnetism.In comparision to immobilizing noble metal nanoparticles on the surface of TiO₂ nanofibers,embedding them into the TiO₂ nanofibers can improve light absorption and reduce the recombination of charge carrier more efficiently,which lead to higher photocatalysis performances.In addition,the exsitence of Fe₃O₄ nanoparticles endows the composite materials good magnetism,which can solve the series of issue in separation and recycling.In the chapter ?,we combine the electrospinning technology with the high-temparature calcination method to prepare one kind of MO/TiO₂ composite nanofibers that have a ZnO/TiO₂ heterostructure.The ZnO nanoparticles uniformly distribute inside the TiO₂ nanofibers,resulting in many MO/TiO₂ interfaces.This unique feature can not only improve the light-responsive scope and the light absorption of composite materials,but also can efficiently prevent the recombination of electron-hole pairs and then increase their lifetime.Thereby,the obtained composite materials exhibit enhanced efficiencies of photodegradation and improved photocatalysis performances.In the chapter ?,we combine the electrospinning technology with the hydrothermal method to prepare one kingd of magnetic composite TiO₂ nanofibers modified with Ag Br nanoparticles.The Ag Br nanoparticle,as a typical semiconductor material,can obviously enhance the light-responsiveness and can efficiently capture hot electron,which can further improve the utilization of excited electon and hole.Therefore,as-obtained composite nanofibers show enhanced photocatalysis efficiency.In addition,owing to the exsitence of Fe₃O₄ nanoparticles,the composite nanofibers have good magnetism,which can achieve fast separation and recycling under external magnetic field.In the chapter ?,we develope a novel visible-light-driven photocatalyst Au@Pd@TiO₂ composed of Au@Pd bimetal nanoparticles and macroporous TiO₂?anatase?scaffold via a colloid templated method.Owing to the strong localized surface plasmon resonance?LSPR?effect and the unique macroporous structure as well as the strong interaction between noble metal nanoparticles and semiconductor oxides,the catalyst show excellent catalytic activity and stability in aerobic oxidation of alcohols in water at ambient temperature using air as the oxidizing agent under visible light irradiation.A wide range of substrates,including different primary and secondary alcohols,can all be effectively oxidized to the corresponding aldehydes and ketones with high selectivities.Moreover,the catalyst is easily reusable at least ten times without appreciable reduction of catalytic efficiency.The green catalytic conditions and the outstanding catalytic performances make Au@Pd@TiO₂ a potential material for practical applications in the selective aerobic oxidation of alcohols.