Preparation And Photocatalytic Performance Of Nitrogen-doped Titanium Dioxide Nanomaterials Modified With Silver

Nowadays,energy shortage and environmental pollution have become two important issues that threaten our normal survival and future development.Titanium dioxide(Ti O₂),as an excellent semiconductor material,has great potential in the fields of solar energy,biomedicine,sewage treatment,and air purification.However,Ti O₂has a relatively wide band gap(3.2e V)and only responds to ultraviolet light,which accounts for only 4%of sunlight;and the electron-hole pairs generated by Ti O₂being excited by light are very easy to recombine.The disadvantages of these two aspects are Photocatalysis has limited the application of Ti O₂.Studies have shown that the use of Ti O₂with special morphology and the doping modification of Ti O₂can solve the above two problems.The main research work is as follows:(1)Nitrogen-doped titanium dioxide(N-Ti O₂)nanomaterials with oxygen vacancy were prepared by hydrothermal method using tetra-n-butyl titanate as titanium source and concentrated ammonia water as sedimentation agent and nitrogen source.The effects of hydrothermal temperature and other factors on the structure and photocatalytic performance of the materials were investigated.Using the analysis methods such as XRD,XPS,SEM,TEM,on the material of crystal structure,morphology,structure and surface features had been used to characterize the various aspects of research,phenol,as one of the difficult to the mineralization of organic pollutants has certain representativeness,therefore with phenol as the goal pollutant,through the research on the removal rate of phenol and mineralization rate of evidentiary materials to improve the performance of photocatalytic degradation of phenol and mineralization ability enhancement.The results show that the material prepared is a mixture of anatase Ti O₂nanorods and nanoparticles,and the N element is effectively doped into the Ti O₂lattice,and there is a certain amount of oxygen vacancy in the lattice.Hot water temperature is 210?in the preparation of nitrogen doped Ti O₂materials containing oxygen vacancy in 5 h after visible light irradiation,removal rate of phenol and mineralization rate is 83.67%,32.16%respectively,in the same way,ultraviolet light condition was100%,80.68%,showed that phenol are more likely to be mine under ultraviolet light into carbon dioxide and water,and the mineralization rate of phenol in visible light is low,there is more in the middle of the product.The results of repeated use test showed that the removal ability could be maintained after 5 times of repeated use.(2)The optimal conditions were selected by orthogonal test and single factor test,and the silver modified nitrogen-doped titanium dioxide(Ag/N-Ti O₂)composite nanomaterials with oxygen vacancy were prepared by hydrothermal method.The characterization and analysis were performed by means of characterization tests.The effects of intermediate products on photocatalytic performance during degradation of phenol were studied.The results show that the photocatalytic activity of the material is improved after the doping of nitrogen and precious metal silver.The best photocatalytic performance of the material is obtained when the ratio of N(Ti):N(N):N(Ag)=1?0.45?0.32.The photocatalytic reaction of the material is consistent with the first-order reaction kinetics equation,which indicates that the material has great potential in the practical application of environmental purification.Under visible light and ultraviolet light,Ag/N-Ti O₂has high photocatalytic activity.Under visible light,the degradation rate of phenol reaches 80.8%within 5h,which is twice that of Ti O₂.Under 2h ultraviolet light,the degradation rate reached 99.3%.In the photocatalytic mineralization of phenol,hydroxyl radical(·OH)has the strongest inhibitory effect on the reaction,and it has been proved that most of the unmineralized intermediate products in the reaction under visible light irradiation are catechol and hydroquinone.(3)A series of Ag/N-Ti O₂composites were synthesized by biological template method and hydrothermal method in the previous work.The Ag/N-Ti O₂composite nanomaterial prepared by hydrothermal method has better photocatalytic removal effect and excellent mineralization ability for phenol than the Ag/N-Ti O₂composite prepared by biological template method.According to the research results in Chapters 2 and 3,the Ag/N-Ti O₂composite material with the best performance of photocatalytic degradation of phenol prepared by hydrothermal method was selected as the photocatalytic material.The photocatalytic degradation of acetaldehyde by Ag/N-Ti O₂composites under different light intensity,pollutant concentration and photocatalyst dosage were studied.