Study Of Microstructure Modulation And Photodegradation Of Gaseous Benzene For TiO₂ Nano Microsperes

The problem of human living environment is becoming more and more serious.However,in recent years,due to the pollution caused by volatile organic pollutants(VOCs),people pay more and more attention to it.The catalytic degradation of VOCs by semiconductor materials is one of the most promising environmental purification technologies.Among many excellent semiconductor catalysts,TiO₂ has become one of the most ideal catalysts because of its stable chemical properties,non-toxic to human body,low price and light energy only.As we all know,the efficiency of nano materials often benefits from its nano size effect,and the regulation of its morphology and size has naturally become the direction of the majority of scientific workers.In this paper,the morphology and microstructure of TiO₂based semiconductors were controlled by simple hydrothermal method.The UV-Vis response of TiO₂ based semiconductors was modified by doping and coating.The photocatalytic performance of gaseous benzene as the standard was studied.The main research contents and results are as follows:1.Four kinds of TiO₂ nanospheres with different morphologies were synthesized by hydrothermal method.TiO₂solid microspheres with secondary structure composed of nano particles were synthesized with large specific surface area and obvious mesoporous structure;TiO₂ hollow microspheres were synthesized by polystyrene(PS)microspheres as template,with high average particle size,large porosity and controllable particle size range.At the same time,surface carbonated TiO₂ hollow microspheres were synthesized by changing the heat treatment atmosphere.By changing the hydrothermal conditions,TiO₂ based nanospheres with yolk structure were synthesized.The microsphere prepared by this method is core-shell structure,with large core-shell distance,and the TiO₂ nanosphere with this structure has good optical absorption efficiency.The Si O₂ microsphere is used to replace the TiO₂microsphere core,and the effect of different heat treatment temperature on the growth and morphology of Si O₂@TiO₂ nanosphere is analyzed.The influence of microsphere morphology on photocatalytic degradation of gaseous benzene was discussed.2.Modification and doping of TiO₂nanospheres with N,F and B elements.The doped TiO₂nanospheres improve the response intensity of UV-Vis light absorption,and the absorption edge also shows a red shift phenomenon in UV-Vis test.Among them,the doping of N and F significantly reduces the band gap width of TiO₂ based nanospheres,and enhances the absorption of visible light.With the increase of B element doping,the UV response intensity of TiO₂based nanospheres decreases,while the visible response intensity increases significantly.XRD test shows that the doping of non-metallic elements(N,F,B)discussed in this paper has a certain influence on the transition temperature of TiO₂ nanospheres from anatase to rutile,and the grain size of TiO₂ nanospheres decreases with the increase of doping amount.By doping different nonmetallic elements into TiO₂ nanospheres,the photocatalytic performance of TiO₂nanospheres under visible light conditions has increased significantly.3.The core-shell nanospheres of V₂O₅@TiO₂ and TiO₂@V₂O₅were designed and synthesized.The effects of hydrothermal temperature and the ratio of coating on the photocatalytic properties were investigated.The heterojunction was formed on the surface of the microspheres with V₂O₅ as the core and TiO₂ as the shell.At the same time,TiO₂ coating affects the crystallinity of V₂O₅.The TiO₂ core does not only increases the specific surface area,but also improves the light absorption efficiency.The heterojunction formed on the surface of the microspheres prepared by the two coating methods can effectively separate photogenerated electrons and photogenerated holes,and broaden the light absorption range of TiO₂ nanospheres.4.Through the comparison of different microsphere morphology and the performance of doped photocatalyst,the influence of the microstructural regulation of TiO₂ microsphere on the photocatalysis performance was determined.The optimal area of photocatalyst in a specific confined space was determined by calculation.The influence of the actual confined environment on the photocatalysis performance was analyzed,and the results were compared with the experimental micro characterization in this paper.The kinetic reaction equations of photocatalyst with different morphology and doping modification were determined.By comparing the photocatalytic reaction rate constant K and adsorption constant k of different materials in the Langmuir Hinshelwood kinetic equation,the difficulty of photocatalytic reaction of TiO₂microspheres with several morphologies was discussed.