Study On The Mechanism Of Active Oxygen Radicals In The Catalytic Oxidation Of NO And Toluene By Different Photocatalyst

With the development of today’s society and economy,environmental pollution and energy shortage are still problems that need to be solved urgently.In particular,environmental pollution is particularly prominent.Among them,air pollution is increasing day by day,and because it is easy to spread and spread,there are difficulties and challenges in control and prevention.According to the Bulletin of the State of the Ecological Environment in China 2019,nitrogen oxides（NOx）are still the main substance causing environmental pollution.Nitrogen oxides（NOx）are the main precursors that cause photochemical smog and acid rain;the air pollution caused by volatile organic compounds is also an urgent problem to be solved,and its small concentration can also cause important harm to the human body.The traditional treatment technology of nitrogen oxides（NOx）is mainly aimed at industrial high-concentration pollutants,but the removal of low-concentration ppb-level NOx is not feasible at the economic and technical level.Therefore,seeking to deal with low-concentration NOx and VOCs air pollutants technology is the key to solving the problem.As a green and environmentally friendly pollutant removal technology,photocatalysis technology can convert solar energy into chemical energy.And it has broad prospects in the degradation of low-concentration toluene and catalytic mineralization into CO₂ and H₂O.The photocatalyst plays a vital role as an important medium for the reaction.In order to improve the activity of the photocatalyst,researchers have proposed a variety of modification strategies,such as adjusting the energy band structure of the catalyst,optimizing the morphology control of the surface structure,and constructing a heterostructure to change the electron transmission.The main decisive role of the photocatalytic reaction process is the reactive oxygen species（Reactive Oxygen Species,referred to as ROS）,the main intermediate in the reaction of the catalyst adsorbing H₂O and O₂molecules.The identification,quantitative qualitative and kinetic evaluation of reactive oxygen species are of great significance for understanding its photodegradation mechanism,improving degradation efficiency,and using various developed technologies for practical applications.Therefore,adjusting the energy band structure of the catalyst can enhance the adsorption and activation capacity of the catalyst surface.Through in-situ infrared technology,real-time monitoring of the conversion of intermediate products into final products in the reaction process is helpful to analyze the reaction mechanism and clarify the modification direction to improve the performance of the catalyst.Therefore,in this paper,a new type of calcium hydroxystannate with a perovskite structure is prepared by modifying carbon nitride and changing the reaction conditions,and adjusting the electronic structure to enhance the photocatalytic performance and promote the adsorption and activation of pollutants on the catalyst surface.We developed a new type of OH/Na co-doped carbon nitride（defined as Na OH-CN）by hydrothermal reaction in a hot alkaline solution to accelerate the separation efficiency of carriers and enhance the redox potential,effectively photocatalytic removal NO.Through experimental characterization and theoretical simulation,a unique directional electron transport channel was established.In addition,the oxygen-containing functional groups appropriately broaden the band structure of CN,reducing the recombination of electrons and holes and improving the efficiency of NO removal.Combining ESR spectra and in-situ drift spectra,the reaction pathway of photocatalytic oxidation of NO was clarified.Therefore,this study provides a new way to guide the random transfer of carriers in CN to improve the separation efficiency and adjust the band structure to enhance the redox capability.For the new type of perovskite-like photocatalyst,the surface hydroxyl defects are caused by changing the reaction conditions,which is conducive to the localization of surface electrons and can improve the separation efficiency of electrons and holes.The hydroxyl defect promotes the adsorption of H₂O on the surface of the catalyst and generates·OH radicals,and its photocatalytic performance is significantly improved.Combining the results of in-situ DRIFTS and DFT simulations,we found that the presence of defects has enhanced adsorption capacity for the intermediate products of benzyl alcohol,benzaldehyde and benzoic acid,which is more conducive to promoting ring opening in benzoic acid,and the intermediate product is on the surface of the catalyst during the reaction.For adsorption activation,it is more favorable to degrade into the final product CO₂.In addition,in the process of photocatalytic removal of NO and degradation of toluene,the accumulation of intermediate products will poison the photocatalyst,causing its recycling efficiency to be affected.At the same time,it also inhibits the photocatalytic performance and restricts the species conversion path.Therefore,we only clarify the mechanism research of the conversion of intermediate products into final products through experimental data characterization,theoretical calculation simulation and other techniques,and explore the generation pathways and functions of active free radicals.In order to achieve the ultimate goal of high-efficiency and harmless degradation of pollutants,this study conducted a photocatalytic reaction mechanism study to control toxic by-products.