Preparation And Properties Of TiO₂ Based Photocatalytic Materials

Titanium dioxide material has been extensively studied due to its excellent properties,making it one of the most mature photocatalyst systems at present.However,TiO2 has wide band gap and only responds to ultraviolet light.This part of the light is less than 5%of the sunlight.It has low utilization rate of visible light and high photogenerated carrier recombination rate.Therefore,titanium dioxide modification has become a significant research work.In order to solve the above problems,this paper mainly uses ion doping to modify titanium dioxide.1.Indium ion modified titanium dioxide powder was prepared by sol-gel method and a series of photocatalysts were characterized.It was found that indium was connected with hydroxyl or terminal oxygen atoms in the form of fixed ions and distributed evenly on the surface of titanium dioxide.Due to the surface modification of indium,the synthesized TiO2 samples have smaller size,larger surface area and a mesoporous structure.When In content was 2.0 mol%,In-TiO2 had the optimal photocatalytic performance,and its hydrogen generation rate was 277.8μmol g-1,h-1,about 23 times that of P25.2.On the basis of indium doping,metal-nonmetal co-doping of titanium dioxide was further performed.The In/C-TiO2 composites were successfully prepared by simple heating method,and a series of photocatalysts were characterized.It was found that the surface morphology changed and mesoporous structure was more obvious.The synergistic effect of indium and carbon can lead to a narrowing of the bandgap of titanium dioxide,which effectively enhances the visible light response and causes a red shift in light absorption.In addition,the impurity level in the titanium dioxide bandgap can be used to promote the separation of the electron-hole pair and improve the lifetime of the photogenerated carriers.In/C-TiO2 showed better photocatalytic performance than pure P25;among them,10%In/C-TiO2 samples had the optimal photocatalytic activity.For the degradation rate of MB,its efficiency reached 95%.3.NiTiO3/TiO2 nanotube heterostructures were synthesized by in-situ method.NiTiO3 was supported on the surface of TiO2 nanotubes.The nanotubes had an outer diameter of 10 nm and a length of several hundred nanometers.Compared with pure TiO2 nanotubes,the heterogeneous structure of NiTiO3/TiO2 nanotubes had enhanced visible light absorption and a higher utilization of sunlight.NiTiO3 was an effective promoter to improve the photocatalytic activity of TiO2.The maximum hydrogen production rate of NiTiO3/TiO2 nanotube composites was 680 μmol g-1 h-1,which was about 15 and 55 times higher than pure TiO2 nanotubes and P25,respectively.For the NiTiO3-TiO2 n-n junction,photogenerated electrons easily migrated from the conduction band of titania to the conduction band of nickel titanate,and the holes migrated in the opposite direction,resulting in the efficient separation of photogenerated electron-hole pairs.Both nanotube morphology and stable heterostructures can result in the separation and transport of photogenerated carriers,leading to high photocatalytic efficiency.