Preparation Of TiO₂-based Photocatalysts And Their Photocatalytic Activities For H₂ Evolution From Water

In recent years, TiO2 nanomaterials have been widely applied in environmental protection, photoelectricity or biomedical fields because of their excellent physical and chemical properties. Especially in photocalysis field, synthesis and properties research of TiO2 has attracted a lot of attention. However, the wide band gap of TiO2 limits it only used under UV light, reducing the utilization of solar energy. Therefore, reseachers try to improve their properties by develop different kinds of TiO2-based nanomaterials to optimize TiO2.Based on the above, some new TiO2-based photocatalysts with low-cost, high efficient and high chemicial stability were studied to improve their phtotcatalytic activies of H2 production from water under UV and visible light illumination. Meanwhile, the photocatalytic hydrogen evolution was studied as a function of concentration of sacrificial agent, pH of solution and content, respectively. At last, the photocatalytic mechanism was preliminarily discussed by electrochemical or other characterization. After systematic study, some interesting results were obtained in this thesis:1. Rutile TiO2 nanosheets were prepared by a simple solvothermal process, and Cu was loaded on the surface of TiO2 nanosheets using the in situ photo-deposition method. TiO2 nanosheets loaded with Cu is an efficient Pt-free photocatalyst with a rate of H2 evolution of approximately 22.1 mmol·g’·h-1 during the first 5 h under UV light irradiation, higher than that of P25 with 9.78 mmol·g-1·h-1 under the same condition. It can be widely applied in practise.2. Au nanospheres/TiO2 composite was prepared by a sol-gel process. It is an efficient photocatalyst with a high rate of H2 evolution of approximately 1.18 mmol·g-1·h-1 during first hour under visible light irradiation. Additionally, the size of Au nanospheres and content of Au are the two key paramters affecting the hydrogen production. The results indicated that the rate of H2 evolution gradually increases with increasing the size of Au nanospheres and the content of Au, and thereafter begins to decrease. It may be closely related to the change of plasmon resonance absorption induced by the size of Au nanospheres.3. TiO2/TiF3 bule powder composite was prepared by a simple solvethermal process. This composite is a new photocatalyst for the photocatalytic H2 evolution from water under visible light irradiation. Its rate of H2 evolution is up to 2.80 mmol·g-1·h-1 under solar light illumination. TiF3 molecule serves as a sensitizer to make TiO2 absorb visible light or infrared light, improving the photocatalytic activities of H2 production from water. Therefore, TiO2/TiF3 composite can serve as a potential photocatalyst.