Preparation And Visible Light Photocatalytic Activity Of La/Ce Modified TiO₂

Nowadays, environmental pollution has become one of the problems which always plaguing human sustainable development. In recent years, fog and haze emerged has alarmed to us that the bad environment threats to our health. Environmental pollution should be governed immediately. So a large number of man power and resources have been used to seek a proper method for solving them. From the 1970 s, the development of semiconductor photocatalytic technology has brought a new life to the solution to environmental pollution. Among those semiconductor oxides, titanium dioxide is the best choice because of its strength oxidation ability, chemical stability, cheapness and easy acquisition. And those advantages made it become an environmentally friendly photocatalyst. However, its two disadvantages greatly limit its application. One is that it can only be excited by UV light whose wavelength is less than 387 nm. Another one is that the recombination rate of photo-generated charge carrier is fast extremely.For the research of the modification of titanium dioxide, doping with rare earth metals is a more effective and economical means. Nanotube titanic acid(NTA) is considered as an excellent precursor for the preparation of titanium dioxide due to its large specific surface area, strong ion exchange capacity, and its derivative possessing the single electron of oxygen vacancies, This article includes the preparation of highly active photocatalysts based on the excellent properties of nanotube titanic acid and the special electronic structure of rare earth metal. Specific studies are as follows.Firstly, Ce-modified titanium dioxide was prepared using NTA for titanium precursor by hydrothermal-calcination method. 0.1% CeOx/TiO2 shown much greater effects for the degradation of MB and colorless organic compounds chlorophenol than commercial P25 under visible light irradiation. Rare earth metals Ce was found existence on the surface of titanium dioxide, which could broad visible light absorption by a series characterizations. And Ce 4f orbitals play a special role in the separation process of photogenerate carriers.Second, La, N doped titanium dioxide was prepared with NTA as titanium precursor. Degradation rate of propylene under visible irradiation is up to 35%, much higher than La, N doped P25. According to the experimental results, a possible mechanism is proposed. The higher visible light activity attributed to the following three points. Firstly, the visible light absorption was expanded by the high concentration of oxygen vacancies. Secondly, the presence of lanthanum oxide and larger surface area of titanium dioxide could absorb more contaminants, which favor for the decomposition of pollutants. Thirdly, defects produced by doping could improve the separation rate of carriers.