Oxidative Modification Of Oxygen Vacancies On TiO₂ And Its Effect On Gas Sensing Properties

In recent years,the atmospheric environment in China is facing a very serious situation,mainly presents with concentration of suspended particles in the atmosphere of the city of sulfur dioxide pollution exceed the standard material;still maintained at a high level;the total emission of vehicle exhaust pollutant increased sharply in the city;nitrogen oxide pollution is aggravating trend.Therefore,it is particularly important to detect all kinds of gases in the atmosphere and their concentration.Therefore,it is particularly important to detect various gas components and their concentrations in various atmospheres.It has become a hot research by many scholars ambient gas component detecting optical sensitive material.The research ideas of this paper are as follows:First compare the surface oxidation of TiO₂?110?,SnO₂?110?and GeO₂?110?surfaces.TiO₂ was found to be most effective for the detection of hydrogen halide gas by the adsorption properties of HF,HCl,and HBr in the three metal oxides.For the three oxides,the surface oxidation is the strongest,and it is an ideal optical gas sensitivity for hydrogen halide gas.Sensing material.At the same time,it was also found that TiO₂ also has good optical gas sensing properties for reducing gas attached H₂S molecules.This article further studied how to improve the sensing characteristics of TiO₂ by doping.The gas-sensing effect of NH₃ on the surface of TiO₂?101?doped with non-metal C,N,F is found to be significantly improved,and the contribution of impurity elements to the oxygen vacancies of the substrate is analyzed.The doping of F element on the surface of the substrate containing TiO₂?101?makes its utilization in the visible light range 5 times higher than that without doping,which is a feasible doping method.The specific research content and process are as follows:1.The oxidation performance,charge population distribution,differential charge density,density of states,and optical properties of rutile TiO₂?110?,SnO₂?110?and GeO₂?110?surfaces were calculated.The calculation results show that after the adsorption of HF,HCl and HBr on the surface of the three metal oxides,the number of electrons lost in the halogen atoms varies,but it is consistent with the adsorption energy and the adsorption distance,which shows that the charge and loss of halogen atoms are The core factors of the adsorption energy and the adsorption distance,the oxidation of the surface of the metal oxide are closely related to the overall gain and loss of electrons,and the charge transfer of the halogen atom is the core factor affecting the adsorption energy,adsorption distance and optical sensing properties.Therefore,TiO₂ can be used as an ideal optical gas sensing material for the detection of hydrogen halide gas.2.The stable structure,density of states,optical properties,and charge distribution of H₂S molecules adsorbed on the anatase TiO₂?101?surface were calculated.It was found that H₂S molecules are not easily adsorbed on the surface of intact TiO₂?101?,but adsorbed on the surface of TiO₂?101?containing oxygen vacancies;adsorption energy ratio of H₂S molecules placed on the surface of TiO₂?101?Adsorption energy of H-end adsorption and S-end adsorption are both large,and the adsorption energy level of aerobic vacancy is placed the largest;in the visible light range,H₂S adsorption on the surface of anatase vacancies TiO₂?101?greatly enhances the utilization of visible light.Rate,as the wavelength increases,the better the use of visible light.Therefore,surface oxygen vacancies will increase the optical sensing effect of the TiO₂ surface.3.Calculation of the surface structure of anatase TiO₂?101?surface-doped non-metallic C,N,F oxidation properties and surface structure stability,density of states,charge distribution,differential charge density,optical properties of adsorbed NH₃ molecules adsorption Happening.The results show that non-metals C,N,and F are easily incorporated into the surface of anatase TiO₂?101?with oxygen vacancies,and the NH₃ molecules are adsorbed on the C and N doped surfaces.Since the number of C and N electrons is smaller than that of O,it is improved.Oxygen vacancy oxidation performance,but can provide even fewer electrons excited by visible light,so reduce the utilization of the material in the visible light range;while adsorbed on the F element doped surface,due to F more electrons than O,reduced Oxygen vacancies are oxidative,but they provide more electrons that can be excited by visible light,making their utilization in the visible range better than C and N doped surfaces.Therefore,surface-doped non-metallic elements significantly enhance the gas sensing effect of TiO₂.This also provides a theoretical basis for further study of the gas sensing properties of the material.