Preparation And Photocatalytic Activity Of Composite Nano-TiO₂

With the over-exploitation and utilization of resources,environmental problems have become more and more serious.Photocatalytic technology has been widely used as one of the important ways to solve this problem.Titanium dioxide has become a widely studied photocatalytic material due to its non-toxicity,chemical stability and corrosion resistance.However,the technical problems of low quantum efficiency and low solar energy utilization of titanium dioxide limit its application.In this dissertation,the research on the preparation of porous,nano-sized and composite titanium dioxide from ethylene glycol and tetrabutyl titanate is carried out.The purpose of this paper is to study the application of new processes and new methods in the preparation and compounding of titanium dioxide,and to expand the application of titanium dioxide.Through the analysis and discussion of its microstructure,structure and performance,the following conclusions are drawn:(1)Porous titanium dioxide is prepared by irradiating-calcining the intermediate ethylene glycol titanium.The prepared porous titanium dioxide is a micron-sized rod with nanometer pores and a large specific surface area.The nano-scale pore is not a stacked pore,the specific surface area of 92.3 m~2/g and an average pore diameter of4.9 nm.Therefore,the porous titanium dioxide has strong adsorption capacity,sedimentation performance,and lower photoinduced carrier recombination opportunity,and the degradation performance of methyl orange is excellent.In addition,the doping of nitrogen atoms has an effect on the crystallinity of ethylene glycol titanium,and simultaneously destroys the Ti-O-Ti bond in ethylene glycol titanium;when the amount of N-doped is 0.25%,the photocatalytic performance of porous titanium dioxide under visible light is the most Excellent and superior to P25,but its ability to catalyze visible light is limited.(2)The preparation of nano-anatase titanium dioxide by low-temperature one-step method is proposed for the first time.The particle size is about 5 nm,the crystal structure is nanocrystalline mixed with a certain proportion of amorphous,and the specific surface area is 504.4 m~2/g.The degradation performance and cyclic stability of methyl orange are similar to that of P25.The preparation process has the advantages of low preparation temperature,short time,no calcination and no need for a high-pressure reactor environment,and is advantageous for further promoting the application of the titanium dioxide photocatalyst.On the basis of this process,a titanium dioxide film was successfully prepared with a thickness of about 300 nm and a surface roughness of 13.6nm.After calcination,the adhesion and density of titanium dioxide thin films were improved,and the photocurrent was further enhanced.In addition,the band gap width of titanium dioxide and carbon nanotubes is reduced by the combination of titanium dioxide and carbon nanotubes,which greatly reduces the probability of electron-hole recombination,thus forming heterojunction.The degradation performance of methyl orange under visible and ultraviolet light is the best,which is superior to commercial P25.(3)Silver phosphate was prepared from silver nitrate and hydrogen phosphate diamine.The effects of preparation temperature,dilute nitric acid and ammonia water on the morphology and properties of silver phosphate were investigated.The silver phosphate solves the problem of poor degradation ability of silver phosphate on anionic degradation products.From the microscopic morphology analysis,the morphology and particle size of silver phosphate affect its photocatalytic properties;from the crystal structure analysis,the photocatalytic performance of silver phosphate mainly depends on the(110)crystal plane.By the combination of silver phosphate and titanium dioxide,the electron-hole recombination probability is lowered,and the photocatalytic performance is improved.After KH-570 modification,the photocatalytic performance is further improved,and the cycle stability is further improved.Increasing,the degradation rate of methyl orange under visible light remains above 90%after three cycles.(4)The surface of titanium dioxide was coated with nickel-phosphorus alloy by irradiation electroless plating method.The specific capacitance reached 562 F/g,which showed the capacitance of Faraday tantalum.After two thousand cycles of charge and discharge,the capacitance remained at about 80%.Its electrochemical stability is better.Nickel-phosphorus-coated titanium dioxide as a Faraday tantalum capacitor solves the problem of large internal resistance and poor electrochemical activity to a certain extent,but further improvement of the process stability and subsequent performance of irradiation electroless plating is needed.The dissertation has 90 pictures,9 tables,and 138 references.