Study On Fabrication、Modification And Photocatalysis Of TiO₂ Nanowires

The increasing water pollution problems is not only limit the economic development, but also threaten the survival of mankind. Since global water resources can not increase, so we have to manage to clean and reuse the wastewater. There are a wide variety of pollutants in wastewater, The larger particles and bacteria can be removed by physical and biological methods; Plasma-chemical methods is available to remove heavy metal ions; For dissolved organic matter in water, photocatalytic methods has proven to be one of the most effective methods. Nowdays, TiO2 is proved to be the most commonly photocatalysts. However, TiO2 can only absorb ultraviolet light in sunlight. Therefore, researchers have employed a lot of modifying and doping approaches to improve the photocatalytical efficiency of TiO2 in visible light.The goal of this study is to dissolve the problem that how to increase the photocatalytic activity of TiO2 under visible light. The thesis is consisted by the following two parts:In part one, two types of TiO2 nanowires were prepared by using Ti sheets and TiO2 nanoparticles. The morphologiesi of the resulted samples were characterized by SEM. The TiO2 Nanowires prepared via TiO2 nanoparticles had better structure, and thus are suitable for the further modification.The crystalline and light-adsorption property of the as-formed TiO2 Nanowires were analyised by using XRD and UV-vis adsorption spectra. Results show that the crystalline of TiO2 Nanowires is anatase, and their absorption in visible-light region is low.In part two, our work is focused on the modification of TiO2 nanowires by Ag3PO4 nanoparticles. We have tried several approacheds to modify Ag3PO4 nanoparticles onto TiO2 nanowires to prepare hierarchical structured AgsPO4/TiO2 Nanowires. By investigating the degradation of AO7 under visible light, Ag3PO4/TiO2 (Ag3PO4:TiO2=1:4)nanowires prepared using in-situ precipitation method at high temperature has the best photocatalytic ability. In order to reduce the cost of nanomaterials and increase the photocatalysis activity of Ag3PO4/TiO2, Ag nanoparticles were modified onto the Ag3PO4/TiO2 nanowires (Ag3PO4:TiO2=4:1 and 2:1) to formed the Ag3PO4/Ag/TiO2 nanocomposites. The as formed Ag3PO4/Ag/TiO2 nanocomposites were characterized by scanning electron microscopy, x-ray diffraction and x-ray photoelectron spectroscopy and UV-vis spectra The degradation of AO7 was test under visible light by using Ag3PO4/Ag/TiO2 nanocomposite as photocatalyst. Nanowire composite was characterized. The reusable ability of the Ag3PO4/TiO2 nanowires were carried out by using Ag3PO4/TiO2 nanowires (Ag3PO4:TiO2=1:4) in recycling photocatalytical experiments to show their. The results showed that after 1 min UV-irradiation induced Ag+ reduction process, the sample (with the ratio of Ag3PO4:TiO2=4:1) exhibited the best photocatalytic properties; and the samples (Ag3PO4:TiO2=2:1) treated by the NaBH4 solution(0.2 mmol/L 200 μL) also has the best photocatalytic performance. Photocatalysis experiments with different content of photocatalyst displayed that the photocatalytic effeciency was increased at higher photocatalyst concentration. The recycling experiments showed that the as-formed Ag3PO4/TiO2 nanowire can be repeatedly used in the photocatalytical reactions for many times, and the 90% AO7 was photodegraded in the first 10 min.