New Technology And Reaction Mechanism Of NO_x Photocatalytic Oxidation-reduction Treatment

Due to the rapid development of society,environmental problems are becoming increasingly serious,bringing severe challenges to human sustainable development.needs.NO_x is a widespread air pollutant,which not only seriously endangers human health but also causes ecological and environmental problems.Therefore,it is urgent to develop green and efficient NO_x treatment technology.Photocatalytic technology has received widespread attention in the field of NO_x purification.Currently,researchers have achieved photocatalytic oxidation of NO_x to nitrate（NO₃^-）under mild conditions.However,the NO₃^-produced in the NO_x oxidation process is poorly stable and has the potential risk of diffusion into the atmosphere or transfer to water by rainwater,causing secondary pollution.The ideal purification of NO_x is to convert it into harmless nitrogen（N₂）with high efficiency and selectivity.But the direct reduction of NO_x to N₂ is energy intensive and owns low efficiency.Therefore,it is a promising strategy to oxide NO_x to stable NO₃^-by photocatalysis,followed by photocatalytic selective reduction of the generated NO₃^-to N₂,which can achieve low energy consumption and high efficiency of NO_x harmless purification.In this thesis,a Bi OI photocatalyst modified by intercalation of the-OH group was designed to achieve an efficient photocatalytic NO_x oxidation reaction.In combination with various characterizations and theoretical calculations,the results show that the-OH group intercalation changes the electronic structure of the catalyst,making the surface iodide ions（I^-）leave the equilibrium position and become active sites,promoting the adsorption activation of NO molecules on the photocatalyst surface,lowering the reaction potential of intermediates,accelerating the interlayer photogenerated electron-hole transfer,and finally oxidizing NO to the NO₃^-efficiently.Subsequently,the efficient and highly selective conversion of NO₃^-to N₂ was achieved by introducing the formic acid（HCOOH）oxidation reaction instead of the water oxidation reaction based on the P25 photocatalyst.Further,based on the photocatalytic NO₃^-purification in real scenarios,the effect of coexisting pollutant ionic chlorate（ClO₃^-）on the NO₃^-purification reaction process was systematically investigated.And various in-situ characterization experiments and theoretical calculations were applied to investigate the interactions between individual and co-purification.The results show that the presence of ClO₃^-promotes the photocatalytic oxidation reaction of HCOOH to produce strongly reducing CO₂^·-radicals.Subsequently,the intermediate coupling-decoupling route from NO3-reduction and HCOOH oxidation is enhanced,which finally accelerates the NO₃^-reduction and achieves the efficient conversion of both mixed pollutants（NO₃^-and ClO₃^-）into harmless products（N₂ and Cl^-）.