Preparation,Modified And Photocatalytic Performance Research Of TiO₂ Nanomaterials

With the continuous improvement of people's living standards,more and more products originate from non-renewable natural sources such as petroleum,coal and natural gas.At the same time,the various steps of the extraction,transportation,and transformation of raw materials into final products are likely to bring negative effects to the environment.Therefore,environmental pollution and energy shortages become a global problem that human beings are currently coping with.The achievement of semiconductor photocatalytic technology in the field of environmental remediation can not be ignored.It has been proved that the technology is an effective way to degrade the harmful pollutants in water and atmosphere.Solar cells and solar photocatalytic H2 production through water splitting can achieve the efficient use of renewable energy to solve the problem of energy crisis.Titanium dioxide is considered to be a very ideal photocatalytic semiconductor material because of its high stability,non-toxic and low cost.The surface area of photocatalyst is an important factor to determine the adsorption capacity of pollutants,which directly affects the strength of photocatalytic activity.Because of the high surface energy of the nanometer material,the nano-particles tend to accumulate to achieve the equilibrium state of the system,resulting in the serious agglomeration of the nano-powder and the small active surface area.Therefore,it is necessary to use a surfactant as a dispersant and to optimize the preparation process to obtain a homogeneous dispersion of titanium dioxide with nanostructures.The main research contents are as follows:1.Combining with the advantages of the sol-gel method and solvothermal method,this paper adopts the sol-solvent thermal improved process for experimental analysis.According to the ratio of reactants,the nanometer titanium dioxide is prepared by using butyl titanate as titanium source,anhydrous ethanol as solvent and concentrated nitric acid as inhibitor.2.The effects of solvothermal temperature,solvothermal time,calcination temperature and calcination time on the photocatalytic activity of titanium dioxide are investigated by means of single factor experiment and orthogonal experiment,according to the photocatalytic degradation rate of methyl orange.The result of the orthogonal experiment shows the optimum process parameters for the preparation of nanometer titanium dioxide.The photocatalytic degradation rate of the sample prepared under the conditions of solvothermal temperature of 150?,solvothermal time of 24 h,calcination temperature of 450? and calcination time of 4h is the highest,which is 82.88%.In the meantime,the XRD,SEM,TEM and EDS images show that the sample is a single anatase phase with good crystallinity and without any impurities,but the dispersibility is general.3.On the basis of the optimum process parameters,the optimum ratios of different types of surfactants are explored by controlling the species and contents of the surfactants to determine the best dispersant for the modification of titanium dioxide nanopowders.Meanwhile the samples are characterized by XRD,SEM,TEM and EDS.The following experimental results are obtained.The optimum ratios of the different types of surfactants?the mass ratios of surfactants to butyl titanate?are respectively: cationic surfactant CTAB of 1:60,anionic surfactant SDBS of 1:30,and nonionic surfactant PEG of 1:30.Under the optimum ratios of different types of surfactants,the photocatalytic degradation rates of CTAB modified nano-TiO₂,SDBS modified nano-TiO₂ and PEG modified nano-TiO₂ compared with unmodified nano-TiO₂ are improved by 16.28%,13.41% and 9.23%,respectively.The samples are pure and have a good crystallinity of a single anatase phase.In addition,the modification effect of CTAB is significantly better than that of SDBS and PEG,which makes the nanoparticles uniformly dispersed.