| TiO2 photocatalytic technology has a broad application prospect in reducing environmental pollution by utililzing solar energy at room temperature,due to its oxidation and decomposition of pollutants, However, the band gap TiO2 is 3.2eV, corresponding to the ultraviolet part of sunlight which only accounts for only 3-4%. It is difficult for large-scale practical application of TiO2 photocatalys.An effective approach to shift the optical response of TiO2 from the ultraviolet to the visible spectral range is to dope TiO2 with nonmetal,rare earth ions and SiO2. Rare earth ions and nonmetal ions co-doped TiO2 nanowires were prepared by electrophoretic deposition method. The photocatalytic degradation of methyl orange solution was used as model reaction to evaluate the photocatalytic activity of those TiO2 nanowires doped with Nd3+, Ce3+ and N,F, and doped with silica.The results show that the nanowires doped with Ce3+ and F- has the maximum photocatalytic activity. The photocatalysts were characterized by UV-Vis, XRD and SEM. The results showed that the absorption edge of Ce3+/F-/TiO2 shifts remarkably toward longer wavelength, and the catalyst exhibits the stronge absorption for visible light. The average grain size for Ce3+/F/Ti02 is about 4.6nm, and the nanowires were dispersed. The TiO2 nanowire is composed of anatase and rutile. F- doping can increase the photocatalytic activity of TiO2 The crystal size of the TiO2 particles was restrained, leading to the separation of electrons and hole when Ce3+ was doped. At the same time, the average grain size is 10nm for F/SiO2/TiO2 nanowire which was evenly dispersed.The incorporation of silica makes the TiO2 nanowire stable, smaller and easier to disperse. F-ion incorporation can effectively reduce the grain size, so as to achieve the purpose of improving the photocatalytic efficiency.For module reaction, the photocatalytic degradation of methyl orange solution was investigated. The effects of calcining process and concentration of Ce3+ and SiO2 on the photocatalytic activity were evaluated. The optimum preparation conditions with the highest photocatalytic activitys were obtained with calcining temperature of 500℃, soaking time of 2 h, and Ce3+concentration of 0.4mol%. Under the condition of 1 h irradiation, the degradation ratio exceeds 95%. For TiO2 nanowire doped with silica, the optimum preparation condition with the highest photocatalytic activity for the degradation of methyl orange solution were obtained with calcining temperature of 500℃, soaking time of 2.5 h, and silica concentration of 2mol%. Under the condition of 45 min irradiation, the degradation ratio is about 95%.
|
PDF Full Text Request