Photocatalytic Oxidation Of Perovskite-Type Catalysts To Atmospheric Pollutants NO

Soil produces nitric oxide（NO）in nature,and these NOs reduce air quality as well as ozone concentrations in the atmosphere,causing acid rain,endangering human health,damaging soil and plants,and other serious problems.At present,there are scientific researchers seeking an effective green technology to remove such pollutants,to achieve the effect of protecting the environment.At present,a wide range of sunlight has been used for photocatalytic oxidation of highly diluted NO in the air.For photocatalytic reactions,it is very important to find a high-efficiency,low-cost and high-stability photocatalyst.Therefore,scientific researchers have invested a lot of energy in the research of catalysts.In the photocatalytic process,a photocatalyst irradiated by sunlight can oxidize NO to nitrate ions（NO₃^-）.In recent years,perovskite materials have been favored by many researchers,mainly because perovskite materials have very important technical properties,they have applications in photocatalytic performance,thermistors,gas sensing,solar conversion,rechargeable batteries,nonlinear optics and fuel cells,so such perovskite photocatalysts have been widely concerned by researchers,but due to their own wide band gap and other shortcomings limit their application in photocatalytic NO oxidation.In this paper,the perovskite catalysts CaTiO_3-δ（CTO）and Cs₃Bi_2-xPb_xBr_9-xwere mainly used as research objects,and CTO and Cs₃Bi_2-xPb_xBr_9-x materials were successfully prepared by solid-phase method and co-precipitation method,respectively.By constructing heterojunctions or ion doping to improve their absorption of visible light and their photocatalytic activity,thereby improving their efficiency of NO oxidation and in-depth exploration of their photocatalytic oxidation of environmental pollutants NO.Firstly,V_O-containing CTO was prepared by solid-phase method in air at 1300 ℃.The adsorption behavior of other gas molecules（H₂,H₂O,CO₂）other than NO/NO₂ on the surface of CTO was studied,and their effects on the photochromism,visible light absorption,thermophore carrier transfer and NO₂ oxidation effect of pollutants in the atmosphere were also discussed.The results show that CO₂ adsorption can cause CTO to produce an intermediate gap state,and can enhance its light absorption of visible light at wavelength 482 nm(A₄₈₂)and can cause CTO to produce photochromism.The results show that photocatalytic NO oxidation in humid air,V_O on the surface of CTO can not only promote the adsorption of NO₂ intermediates but also promote the further oxidation of NO₂,and the phenomenon of photochromic caused by CO₂ gas sensitization is more conducive to the activation and conversion of O₂ into superoxide ions（·O₂^-）in dry air.Calcining the sample in 5%H₂-Ar（5%H₂）accelerates the desorption of CO₂ on the CTO surface,allowing the CTO to indicate that more VO is produced to induce photocatalytic reduction of H₂O in humid air.This paper shows that V_O in perovskite can greatly improve the adsorption affinity of NO and NO₂,while its effect on the adsorption of H₂O,H₂ and CO₂ is less obvious.In addition,according to the calculations,the results show that CO₂ is more easily adsorbed on a single Ti-O layer than on the Ca-O layer,and CO₂ can also activate on the surface to produce hydrocarbons（CH₄,CH₃OH and HCHO）that change the surface properties of the photocatalyst,which has been neglected in previous environmental photocatalysis studies.The Z-shaped heterojunction of CTO and CuO showed that the constructed heterojunction showed higher NO oxidation efficiency（64%）when the visible wavelength>450 nm,indicating that the constructed heterojunction showed a stronger photon utilization rate（0.046%）when the visible wavelength was>450 nm.Secondly,Cs₃Bi_2-xPb_xBr_9-x with different Pb contents was prepared by co-precipitation in this paper,in order to reveal the correlation between photocatalyst oxidation NO and Pb²⁺doping.This paper shows that the doping of Pb²⁺not only produces more Br vacancies（VBr）on the surface of Cs₃Bi_2-xPb_xBr_9-x,but also enhances its absorption of visible light,and the doping of Pb²⁺（x=0.0443）also improves its efficiency of NO oxidation（80%）.In addition,since the doping of Pb²⁺produces more V_Br,it also enhances its adsorption/oxidation of NO,and promotes the selective conversion of NO to ionic species N₂O₂^2-rather than toxic NO₂,N₂O₂^2-is generated when two HNOOs are adsorbed on V_Br and coupled and reduced to thermoreceptors,the generation of N₂O₂^2-can passivate the activation of NO on V_Br,thereby reducing the oxidation of NO by photocatalysts.At the same time,in this work,we also found for the first time that Cs₃Bi_2-xPb_xBr_9-x can induce the production of N₂O₂^2-under visible light due to the coupling of V_Br,which is the main reason for hindering the conversion of NO to NO₂,and the formation of N₂O₂^2-intermediates is of great significance for the analysis of the oxidation of NO in future research.In summary,the research content of this paper is to explore high-efficiency photocatalysts and explore the mechanism of photocatalysts on NO oxidation.The results of this paper not only open a new way for the photocatalytic oxidation of NO on the gas-solid interface of perovskite-type photocatalysts containing defects,but also provide new ideas for gas sensitization on solid semiconductors,and provide novel and interesting ideas for perovskite-type catalysts to oxidize atmospheric pollutants NO,and provide new catalysts for the oxidation of pollutants NO in our agricultural environment.