Preparation Of Metal Doped TiO₂ Nanotubes And Photocatalytic Reduction Of CO₂

In recent years, with rapidly industrial development, people are faced two problems:the increasing shortage of renewable energy and the environment are seriously polluted by chemical production. However, these problems could be solved by using a series of chemical products which prepared by photocatalytic reaction. With the merits of non-toxic, low-cost and High-performance catalytic activity, Nano-TiO2 catalyst are widely used in the photocatalytic reaction. However, due to the lower utilization rate of Nano-TiO2 for visible light, photocatalytic reaction hve been unable to industrialization. Therefore,the granular structure of TiO2 have been changed to improve the photocatalysis by physical or chemical methods, for example, nanotubes, nanotubes, nanowire and nanofilm.In this work, the nanoparticle TiO2 was prepared with tetrabutyl titanate (TNB) by modified sol-gel method. The effect of the ratio of reactants, reaction time, reaction temperature and calcination temperature on preparation of nano-TiO2 were investigated in the single factor experiment The Nano-TiO2 catalysts were characterized by XRD, BET, SEM, TG/DSC and UV-Vis spectroscopy. The results showed that structure of nano-TiO2 was anatase, average diameter size was 94.2 nm, surface area was 54.31 m2/g and the optimal calcinations temperature was 500℃. Moreover, the ultraviolet absorbability of nano-TiO2 was more significant than visible light.The TiO2 nanotube was prepared with TiO2 doped with metal ions:Fe3+, Cu2+, Cr3+, Co2+, Al3+ by hydrothermal method. The influence of calcinations temperature, dosage of raw material, synthesis temperature and time on photocatalytic performance of TiO2 nanotube was investigated. Result of SEM showed that TiO2 nanoparticle transformed into nanotube with hydrothermal treatment, the diameter of nanotube was smaller than 30 nm, the length of nanotube was more than 500 nm. XRD showed that the structure of TiO2 nanotube was anatase. The surface area was 154.3 m2/g by BET characteristic, and the optimal calcinations temperature was 300℃by TG/DSC, Uv-Vis spectroscopy showed that TiO2 nanotube had better photocatalytic performance than the TiO2 nanoparticle.In the experiment of photocatalysis, methanol were prepared by photoreduction of CO2 with TiO2 catalysts in self-designed reactor under ultraviolet. The optical reaction conditions were studied by single factor combined with orthogonal design experiments. The results showed that TiO2 nanotube doped with Fe3+, Cu2+, Al3+ possessed remarkable photocatalytic activity. TiO2 nanotube doped with Co2+, Cr3+ had more significant absorption of ultraviolet than visible light, however, it had weaker photocatalytic performance.The reaction kinetics of photocatalytic reduction of CO2 was also discussed. The results showed that the photocatalytic reaction rate equation were C=29.94t0.443 or C=13.7t0.54 when reaction temperature was 30℃or 40℃, respectively. Photoreduction of CO2 was more likely occured upon the addition of TiO2, the energy barrier of reaction of photocatalytic reduction of CO2 was decreased, which made the photoreduction of CO2 be more likely occurred.