Study On Preparation And Performance Of Titanium Dioxide-based Composite Photocatalyst

Among the problems of environmental pollution,the crisis of water pollution has become increasingly prominent.Photocatalytic technology is an effective means to convert clean solar energy into green chemical energy.It has attracted widespread attention from domestic and foreign researchers and has broad prospects for development.Due to the advantages of convenient source,non-toxicity and chemical stability,TiO₂ has shown great potential in applications in related fields.However,the low visible light utilization efficiency and high photogenerated electron-hole pair recombination rate reduce the photocatalytic activity of TiO₂.Based on this,this article uses a combination of multiple modification strategies to study the modification of TiO₂.The main research results are as follows:（1）Using 3-amino-1,2,4-triazole as the precursor,g-C₃N₅ is preferentially prepared by thermal polycondensation method.Subsequently,the TiO₂/g-C₃N₅composite photocatalytic material was prepared by hydrothermal method and high temperature calcination method.X-ray diffraction analysis,transmission electron microscopy,diffuse reflectance spectroscopy and fluorescence spectroscopy were used to characterize the crystallinity,morphology and light absorption properties of the TiO₂/g-C₃N₅ composite;methylene blue and tetracycline hydrochloride were used as the research objects.Characterization of photocatalytic performance.The results showed that the degradation rate of methylene blue（MB）reached 91.5%and the degradation rate of tetracycline hydrochloride（TCH）reached 92.4%in 105 min.The high degradation rate can be attributed to the effective combination of the introduced TiO₂ and g-C₃N₅ to form a heterojunction,With the excellent visible light response characteristics of g-C₃N₅,the photocatalytic performance is significantly improved.Further mechanism experiments confirmed that photo-generated holes（h⁺）and superoxide radicals（·O₂^-）play a major role in the photocatalytic degradation process.（2）A heterojunction photocatalytic material（Sm-TiO₂/g-C₃N₄）coupled with rare earth metal samarium（Sm）doped TiO₂ and g-C₃N₄（Sm-TiO₂/g-C₃N₄）was prepared by hydrothermal method and calcination method.In addition,the effect of Sm doping and g-C₃N₄input ratio on the photocatalytic performance of TiO₂was systematically studied.It was found that the doping of Sm and the constructed g-C₃N₄ heterojunction significantly improved the photocatalytic performance of TiO₂.The best sample（0.5%）Sm-TiO₂/g-C₃N₄can reach 91.8%of the photodegradation efficiency of methylene blue（MB）after 120min of light,which is 6.5 times and 4.7 times that of pure TiO₂and pure g-C₃N₄;for hydrochloric acid The photocatalytic degradation rate of tetracycline is as high as 93.3%,which is 4.2 times and 2.8 times that of pure TiO₂and pure g-C₃N₄.The photocatalytic mechanism experiment proves that photo-generated holes（h⁺）and superoxide radicals（·O₂^-）are the main active substances in photocatalytic degradation.（3）Using Xinjiang cotton stalks as the biomass carbon source,a two-step method was used to prepare a biomass carbon-doped titanium dioxide and carbon nitride composite photocatalytic material（C-TiO₂/g-C₃N₄）.The input amount and the mass ratio of g-C₃N₄ to TiO₂affect the photocatalytic activity of TiO₂.The results showed that the best composite material of（0.1）C/TiO₂/g-C₃N₄ had a photodegradation rate of 92.6%for methylene blue and 97.3% for tetracycline hydrochloride after 90 min of visible light irradiation.Combined with the results of the mechanism research,it is proved that superoxide radical（·O₂^-）is the main active substance of photocatalytic degradation,and photo-generated holes（h⁺）and hydroxyl radical（·OH） are the secondary active substances.