Preparation And Photocatalytic Activity Of Micro/nano-structured TiO₂ Complexes

As a semiconductor photocatalyst, considerable attention has been focused on TiO₂ owing to its unique properties and promising applications, such as air purification, waste water treatment, self-cleanness, mist prevention, bacillus resistance and so on. However, it is still a great challenge to overcome the problems of low photocatalytic activity and low utilization of sunlight. In recent years, there is a rapid development of the improvement of TiO₂ photocatalyst, including the compositing of semiconductor, the doping of the transition metal ions and the non-metallic ions, the depositing of the precious metals and the sensitizing of TiO₂ surface.In this paper, have been focused on the combination of nanosized TiO₂ and other semiconductors materials based on its disadvantages. Micro/nano-structures ZnO/TiO₂ and CuO/TiO₂ composites photocatalyst were prepared by the hydrolyzation method in the surface adsorption layer of the micron dimentional ZnO and CuO. And the photocatalytic activity of the composites was given as a detailed research. The main contents are as follows:Firstly, the reaction mechanisms, the research progresses and the applications of TiO₂ photocatalysts were reviewed.Secondly, in order to keep light electron and hole prolonging and improve the photocatalytic activity, TiO₂ was composited with ZnO which has the similar band-gap. Zn(Ac)₂ and NaOH are used without further purification, the micron dimentional flower-shape and rod-shape ZnO microcrystallines were prepared through a facile wet synthesis. Additionally, the micro/nano ZnO/TiO₂ composite photocatalyst was successfully synthesized by the surface adsorption layer reaction with these microcrystallines as the carriers.Thirdly, TiO₂ was composited with CuO which has the narrower band-gap to broaden the light response range, separate electron-hole pairs, and improve the photocatalytic activity. In a typical preparation, CuSO₄·5H₂O, NaOH, and C₆H₁₂O₆ were all commercially available and used without further purification, the micron dimentional spherical and cubic Cu2O microcrystalline were prepared at 70℃and atmospheric pressure without any surfactants. After heat treatment, the spherical and cubic CuO were obtained. Then with CuO as the carrier of nanometer TiO₂, the micro/nano CuO/TiO₂ composite was successfully prepared by the surface adsorptive layer reaction.Fourthly, experiments were carried out to test the photocatalytic activity of the composite photocatalyst. Methyl orange was selected as a representative dye pollutant of industrial wastewaters. The photoreactor was designed with a high-pressure mercury lamp or fluorescent irradiation, and the abtained micro/nano ZnO/TiO₂ and CuO/TiO₂ was added as the photocatalyst into Methyl orange. The experimental results indicated that the flower-shape and rod-shape ZnO/TiO₂ composites showed the best photocatalytic activity with the mole ratio of ZnO:TiO₂ 3 to 1 and 1 to 1. However, the spherical and cubic of CuO/TiO₂ composites gave the best light catalytic performance with the both mole ratio of CuO:TiO₂ 2 to 1. The effects of different concentrations of catalysts and different initial concentrations of methyl orange on photocatalytic activity were also studied using the catalysts which had the best catalytic activity.