Preparation Of TiO₂ Based Photocatalysts And Their Degradation Performance For Toluene

With the emergence of environmental issues,problems with air pollution also received increasing attention.Volatile organic compound pollutants（VOCs）are easy to enter the atmospheric environment due to their volatility,and most VOCs can cause harm to human health.Therefore,it is of great significance to reasonably and effectively handle VOCs gas.Toluene is a representative VOC gas.Due to its molecular structure,it is a difficult to degrade pollutant and can also stimulate the skin and mucosa,damaging the central nervous system.This article uses toluene as the target pollutant for photocatalytic degradation.Photocatalytic oxidation technology has great potential in treating VOCs due to its low energy consumption,low secondary pollution,low cost,and environmental protection.The selection of photocatalysts is the core of this technology.TiO₂ is a representative n-type semiconductor,due to its advantages such as low cost,high chemical activity,stability,and non-toxicity,it is currently one of the photocatalytic materials with large-scale industrial applications.However,pure TiO₂ can only respond to ultraviolet light due to its broadband gap,and the generated photo generated charge carriers are easy to recombine,thus limiting its photocatalytic ability.This article starts from reducing the bandgap energy and increasing the efficiency of photo generated carrier separation.Additionally,because oxygen vacancies can serve as traps and adsorption sites for photo generated charges,the transfer rate of photo generated charges is higher,resulting in more reaction sites.Therefore,a series of TiO₂substrates containing oxygen vacancies have been prepared and applied to the degradation of toluene,evaluating their photocatalytic performance,and exploring the photocatalytic process of toluene degradation.（1）The combination of hydrothermal method and calcination method successfully prepared C/TiO2 photocatalytic materials.Using toluene gas as the target pollutant,the target pollutant was photocatalytic degraded under simulated sunlight conditions using a 300 W xenon lamp.The experimental results showed that the degradation rate of toluene by C/TiO₂ was 95.1%and the mineralization rate was92.3%after 2 hours of illumination.The degradation rate and mineralization rate of toluene by far higher pure TiO₂ were 76%and 59.9%,respectively.which is much higher than the degradation rate（76%）and mineralization rate（59.9%）of pure TiO₂for toluene.After four cycles,the degradation rate of C/TiO₂-3 to toluene can still reach 72.2%,indicating that the material has certain stability.（2）In order to achieve complete mineralization of toluene,a secondary hydrothermal method was used to attempt to codoped TiO₂ with metallic element Mo and non-metallic element S,under simulated sunlight,toluene was used as a target pollutant for photocatalytic degradation.The experimental results show that the effect of Mo and S double element doped TiO₂ is more significant than that of S single doped TiO₂.The degradation rate of toluene by 0.24%Mo-0.5%S/TiO₂reaches 98.3%,and the mineralization rate reaches 98.0%,which is much higher than the degradation rate（76%）and mineralization rate（59.9%）of pure TiO₂ for toluene,and the mineralization effect is more significant.To test the stability of the material,a cycle test was conducted on 0.24%Mo-0.5%S/TiO₂.After four cycles,the degradation rate of toluene can still reach 86.1%.（3）BiOCl（recorded as VOBOC）with oxygen vacancies was prepared by solvothermal induced ethylene glycol reduction method,and VOBOC/TiO₂was formed by simple grinding with hydrothermal calcined TiO₂.Under simulated sunlight,toluene was used as the target pollutant for photocatalytic performance evaluation.The experimental results show that the degradation rate of toluene by 1:3VOBOC/TiO₂ is 99.5%,and the mineralization rate increases to 92.4%,which is much higher than the degradation rate（76%）and mineralization rate（59.9%）of toluene by pure TiO₂.To test the stability of its performance,a cyclic stability test was conducted on 1:3 VOBOC/TiO₂.After four cycles,the degradation rate of toluene by the material can still reach 96.6%.Compared with the previous two experiments,1:3 VOBOC/TiO₂ has more excellent cyclic stability.