Synthesis And Photocatalytic Performance Of Br Doped TiO₂

As a common semiconductor,TiO₂ has low toxicity,low cost and mild reaction conditions.These advantages have contributed to the application of TiO₂ in the visible light photocatalytic degradation of organic pollutants.However,wide applications were limited by its intrinsic drawbacks,such as wide band gap and easy recombination of the photogenerated electrons–holes pairs.An effective strategy is doping additional components in TiO₂ to extending the photo response spectrum to the visible region.In this thesis,Br-doped TiO₂ were synthesized at by the hard template method and solvothermal method.NH₄Br and Na BrO₃ were chosen to be the bromine sources.The Br-doped TiO₂ hollow spheres and Br-doped TiO₂ nanoparticles were prepared by different doping amount of bromine.The optical properties,photocatalytic properties,and growth processes of Br-doped TiO₂ hollow spheres and nanoparticles were investigated and analyzed.The stability,structural advantages,and enhancement mechanism of photocatalytic degradation of RhB,MO and MB by as-preparaed photocatalysts were investigated.The structure and properties of photocatalysts were characterized by X-ray diffraction,Raman spectrum,scanning electron microscope,transmission electron microscopy,N₂ desorption–adsorption,UV–vis spectroscopy,and X-ray photoelectron spectroscopy.The TiO₂ hollow spheres are in diameter of 500 nm and shell thickness of 50 nm.The shell is composed of small anatase grain with size of about 10 nm.The TiO₂hollow spheres exhibit high crystalline and high surface area of 89.208 m²/g.The band gap of as-formed TiO₂ hollow spheres decreased to 2.65 eV.The formation of impurity band in the band gap would narrow the band gap and result in the red shift of absorption edge,further enhances the photocatalytic activity.This work could significantly broaden the potential applications of TiO₂ photocatalysts.The size of the Br-doped TiO₂ nanoparticles would decrease with increasing Br-doping concentration.The minimum size of the nanoparticles is approximately 4nm.The as-prepared Br-doped TiO₂ photocatalyst is composed of the anatase and brookite phases.The Br-doping could efficiently narrow the band gap and broaden the visible-light response region.The dye on the surface of Br-doped TiO₂ could improve the photocatalytic performance during cyclic utilization because of the dye activation.