Photocatalytical Activity And Electrical Conductivity Of TiO₂ Nanomaterials

TiO₂ semiconductor material has been widely used in photocatalytic,solar cells,corrosion-protective coatings etc due to its low cost and chemical and physical stability.Photocatalytic activity of single phase anatase and rutile TiO₂ nanoparticles still has great space for improvement.Previous studies have shown that Anatase-Rutile mixed phase TiO₂ nanoparticles has better photocatalytic performance,doping also could effectively improve the photoelectric characteristics of TiO₂.This work mainly focuses on preparing of Anatase-Rutile TiO₂ by a two-step hydrothermal method and exploring its microstructure and photocatalytic activity.Effect of Zn doping on the photocatalytic activity and electrical property of TiO₂ has also been studied.The main research results are as follows:1,Anatase-rutile TiO₂ nanocrystallines were obtained by adjusting the pH value of the solution and the reaction temperature via a two-step hydrothermal method.The first hydrothermal step was for isotropic growth of nanocrystalline,the second hydrothermal process was for the production of mixed phase TiO₂.The mixed phase TiO₂ showed better photocatalytic activity than that of single phase TiO₂.The reason was considered to be the enhanced dye absorption on the surface of TiO₂ caused by exposure of low crystal indices of rutile phase.2,TiO₂ nanocrystalline powders with various Zn doping levels from Oat%to 10at%were synthesized via sol-gel method with Tetrabutyl orthotitanate?TBOT?and zinc acetate as Ti and Zn source.Zinc doping did not change the structure and absorption band edge of TiO₂,but produced impurity level within the band gap of TiO₂.Low concentration Zn doping could improve the photocatalytic performance of TiO₂,high concentration doping increased the carrier recombination rate which resulted in lower photocatalytic efficiency.The sample with doping concentration of 1%showed the best photocatalytic activity.3,Electrical property of Zn-TiO₂ was investigated through measuring the resistance of Zn-TiO₂ powder annealed at different temperature.The powders were pressed into disks of 200 mm in diameter using a pressure of 10 MPa in steel-made mold,silver glue was brushed on both sides of the disks.It was found that 500 ? annealing processing results in a minimum resistance of Zn-TiO₂ with the identical doping concentration.And 6at%doping has the best effect on decreasing the resistance of TiO₂.Resistance of all doped sample are smaller than that of pure TiO₂.Gels of Zn-TiO₂ with the same doping concentration of the disks were then spin coated onto the surface of glass,light transmittance of the thin films was as high as 90%.From the results we could conclude that phase mixing has a synergistic effect for improving photocatalytic activity of TiO₂,a two step hydrothermal method is an efficient way for producing of mixed phase TiO₂ during which crystals with preferred lattice face growth could be realized.Zn doping has a function of enhancing the photocatalytic activity and electrical conductivity of TiO₂.As for the mechanism of these two process is different,the best doping concentration to get optimum effect is not the same,1%was considered to be the optimal concentration for photocatalytic activity improvement,while 6%was tested as the optimal doping concentration of electrical property modification.The modified TiO₂ nanomaterials is expected to be used in many other applications such as solar cells,water splitting and so on.