Preparation, Characterization And Visible Light-activated Photocatalytic Properties Of A Series Of Titanium Dioxide Catalysts

Recently, the photocatalytic technology has developed rapidly in the control of environmental pollution, sterilization and disinfection, and so on. Organic or inorganic pollutants can be oxidized / reduced to simple nontoxic substances, such as CO₂ and H₂O, at room temperature by employing various photocatalysts with solar energy. Such processes can be carried out under mild reaction conditions with simple equipments. The photocatalytic technology is superior to the traditional catalytic or adsorption technologies in this way. Because of its high chemical stability, environment-friendliness, and relatively economy, TiO₂ is widely used as photocatalyst. However, TiO₂ is a large bandgap semiconductor (～3.2 eV) and becomes active mainly by irradiating with ultraviolet light, which is only 3-5% of the solar energy. Therefore, many efforts have been made to modify or dop TiO₂ in order to improve its photocatalytic activity in the visible light region. Doping TiO₂ with metal or nonmetal ions can effectively reduce the bandgap of TiO₂, and make TiO₂ respond to the visible light. Especially, some oxide complexes composed of metal ions with d⁰ or d¹⁰ configuration have visible-light-driven photocatalytic activities, due to their unique electronic structures. Recently, more experimental data supported that the doping with two metal ions or one metal and another nonmetal ions can further enhance this effect.In the thesis, a series of codoped TiO₂ photocatalysts composed of Ti⁴⁺ with d⁰ and Bi³⁺ with d¹⁰ configuration were prepared as visible-light-driven photocatalysts, and satisfied photocatalytic results were gotten.1. Bi-S-codoped titanium dioxide photocatalysts were prepared using sol-gel method. The doping species and amounts, calcinations temperature, specific surface area and surface state were investigated. The codoped TiO₂ calcined at 400℃exhibits an intense absorption in the range of 500-800 nm. An indigo carmine solution of 20 mg/L was completely photodegraded in 40 minutes in the presence of such photocatalyst under visible light (λ> 410 nm). This highly active photocatalytic performance is associated with the existence of numerous oxygen vacancies, the acidic sites on the surface of TiO₂ and the high specific surface area.2. Bi-S-C-codoped titanium dioxide photocatalysts were prepared using hydrothermal technique by changing the doping amount of bismuch sources and synthetic temperatures. Photocatalytic evaluation results show that the catalyst showed outstanding photocatalytic properties in the visible light region. Indigo carmine solution can be degradated completely in 50 minutes, and other dyes can be also decomposed in a short time.In this thesis, several new codoped TiO₂ visible-light-activated photocatalysts were prepared by using different synthetic methods. These photocatalysts showed a wide visible-light response and high photocatalytic activities. They are expected to be used in degrading wastewater, indoor and other harmful gases, and so on.