Preparation, Photocatalytic Properties On Degradation And Hydrogen Production Of TiO₂-based Nanomaterials

With the advancement and development of society, The hazardous organic pollutants in environment and energy crisis have become an issue of global concern. The researchers are studying one approach can satisfy people’s energy needs and not produce a new threat to the environment. Semiconductor photocatalysis provides a new way to solve the above problems. Among the various semiconductors, titanium dioxide (TiO2) has been widely used in photocatalytic degradation of organic matter and photocatalytic water splitting due to its strong oxidizing power, abundant existence in nature, non-toxicity and long-term physical and chemical stability. However, as a photocatalyst, TiO2 has an inherent drawback that the photogenerated electron/hole pairs recombine fast, which influence the photocatalytic activity of titanium dioxide.In this thesis, the approaches for improving the photocatalysis of TiO2 are proposed:(1) The electrospinning was used to prepare TiO2@SnO2 heterojunction nanotubes which reduce the rate of electron/hole pairs recombination and improve the photocatalytic efficiency; (2) The combustion synthesis was used to prepare TiO2 nanofoams, the enhanced photocatalytic efficiency of TiO2 nanofoams is ascribed to the mixture of crystal (anatase and rutile) and large surface area. And the nanostructure and photocatalytic activities are investigated in detail.1. We have introduced a novel and facile method to prepare TiO2@SnO2 heterojunctions. The TiO2@SnO2 nanotubes and the TiO2@SnO2 nanofibers are prepared by electrospinning. The TiO2@SnO2 nanotubes were calcined for 2h at 500℃ in air at a heating rate of 6℃/min, the TiO2@SnO2 nanofibers were calcined for 2h at 500℃ in air at a heating rate of 1℃/min. The heterojunction nanotubes with a diameter of about 200 nm uniformly distribute SnO2. and TiO2 nanocrystals and present the obvious interfaces between them after calcinations, which form perfect TiO2@SnO2 nanoheterojunctions. The heterojunction nanotubes show high photocatalytic activity for the degradation of RhB dye. Further investigation showed that the TiO2@SnO2 heterojunction, a possible mechanism is proposed to explain the transform of TiO2@SnO2 nanofibers into TiO2@SnO2 nanotubes. This method provides a new approach to prepare composite metal-oxide heterojunction nanotubes.2. A facile method for preparing highly porous TiO2 nanofoams is reported. The nanofoams were prepared in the form of white and loose bubble-shaped by a simple one-pot combustion method. The excellent performance of the TiO2 nanofoams is ascribed to the mixture of crystal (anatase and rutile) and large surface area (～63 m2/g). The TiO2 nanofoams as catalyst showed higher photocatalytic disintegration of RhB and hydrogen production by water splitting than commercial P25 under ultraviolet light irradiation. The excellent performance of the TiO2 nanofoams is ascribed to the photogenerated electrons and holes are separated effectively, the more oxygen and RhB molecules can be absorbed on their surface, the absorption edge of the TiO2 nanofoams was red-shifting compared with the commercial P25 and the TiO2 photocurrent test also shows that carrier concentration increases, the electron hole to improve separation efficiency. These comprehensive factors lead to TiO2 nanofoams have greater photocatalytic degradation and hydrogen Production capacity.