| TiO2film is an important semiconductor functional material because of its characteristics of non-toxicity, high stability, high catalytic activity and no secondary pollution. It has been widely studied and applied in photoelectric conversion, solar energy conversion and storage, and photocatalytic degradation of harmful gases and pollutants in water. In order to improve the photocatalytic activity of TiO2, scientists did a lot of research in the preparation of TiO2film, the factor that affect the photocatalytic activity, and its load technology.This thesis describes the methods for the preparation of TiO2nanowire film on Ti surface by electrochemical oxidation method and liquid chemical oxidation method, and the optimum conditions have been investigated. Meanwhile, TiO2surface morphology, surface structure and its crystal structure have been detected and analyzed by the SEM, XRD and XPS. Using TiO2film as working electrode, saturated calomel electrode (SCE) as reference electrode, Pt electrode as auxiliary electrode, Na2SO4solution as electrolyte,300W simulated sunlight lamp as irradiate source, the TiO2film photoelectric properties were detected in the quartz system by the electrochemical analyzer.The main results obtained in this work are outlined as follows:(1) Under the condition of voltage≤30V, reaction time≤3h, reaction temperature≤80℃and the concentration of NaOH≤2M, the TiO2films prepared by electrochemical oxidation are amorphous and contain a small part of low valence Ti oxide. When increasing the concentration of NaOH to3M, the Ti oxides begin to change into the titanates. When the concentration of NaOH is4M, the chemical the film is mainly titanate. The self-organized net-like structured TiO2film was successfully synthesized when the voltage is30V, reaction time is3h, reaction temperature is80℃and the concentration of NaOH is2M. The photoelectric catalytic activity of TiO2film increased with the increase of the voltage, temperature and concentration of NaOH. And among all of the TiO2films, the net-like TiO2film shows the best photoelectric catalytic activity. This may be related to the net-like structure that can make the light effectively through the mesh and exposure to the bottom layer of the nanowires, and thus the bottom layer of nanowire plays the role in catalytic activity as the surface one.(2) Using liquid chemical oxidation method to prepare TiO2film, we found that:(i) The experimental conditions such as reaction time, concentration of H2O2, NaOH and oxidation time affect the film structure. When the reaction temperature is40℃, the nanowires do not form on the Ti surface. However, when the temperature is too high, the nanowires change to the nanobelts. When the reaction time is not more than1h, the ladder-type sheet structure on Ti surface gradually form with the increase of the reaction time. In addition, the film also can be formed under low concentration of alkaline solution and the nanowires diameter is increased with the increase of the concentration of alkaline solution. When the concentration of NaOH is2M, the nanowire thin film with an obvious net-like structure is obtained.(ii) Using the concentrated ammonia water or Ba(OH)2solution instead of NaOH solution, the uniform nanoparticle thin films, rather than nanowire thin films, are obtained. So the anions and cations in the alkaline solution play a key role in the formation of nanowire film morphology.(iii) After proton exchange and calcination, the films are composed of a mixture of different Ti-contained oxides except that the film surface with sever nanometer in depth is pure TiO2.(iv) The anodic photocurrent measurement indicates that the obtained Ti-contained oxide nanowire films are more photoactive than their precursors and the nanowire thin film calcinated at500℃shows the best catalytic activity. |
