Study On Photocatalytic Properties Of Titanium Dioxide Composite Nanostructures

In the first chapter, a brief overview of photocatalytic technology was firstly presented. The photocatalytic materials what we used in photocatalytic process was introduced next. Then the photocatalytic properties and principles of titanium dioxide photocatalyst were respectively described. In the view of the advantages and disadvantages of these features, some modification methods were introduce, respectively. Coupling TiO₂ with other material, as one of the important modification methods, was emphatically stated. Finally, we briefly described the working idea and research significance of this thesis.In the second chapter, we prepared TiO₂/SrTiO₃ composite photocatalyst through hydrothermal method, and the samples were characterized by XRD, UV-Vis absorption spectra, TEM and XPS methods. The XRD results showed that TiO₂ in composites was composed of anatase phase. UV-Vis absorption spectra revealed that the absorption intensity of TiO₂ was obviously enhanced after coupling with SrTiO₃. Besides the absorption band edge presented little redshift in the composite samples. XPS results confirmed the existence of SrTiO₃ in composite materials, which suggested that TiO₂ was successfully coupled with SrTiO₃. The obvious crystalline interface observed in HRTEM proved that we have successfully synthesized Ti O₂/SrTiO₃ composite materials. The photocatalytic performances of the samples were evaluated by photocatalytic degradation of methylene blue solution. With the increment of SrTiO₃ ratio, the photocatalytic performances of the samples increase and then decrease gradually. The best photocatalytic activity was presented in the sample with 3% SrTiO₃.The variations and mechanisms of the photocatalytic properties in the composite materials were discussed in detail.In the third chapter, we prepared TiO₂/BaTiO₃ composite photocatalyst by the hydrothermal method. The samples were characterized by XRD, XPS, TEM and ultraviolet-visible absorption spectra. The photocatalytic properties of the prepared samples were evaluated by photocatalytic degradation of MB solution. The results showed that the composite samples were mainly composed of anatase phase as the structure of nanotubes. BaTiO₃ attached on TiO₂ nanotubes in the form of nanoparticles. Obvious crystalline interface can be observed from the HRTEM results. No obvious absorption band edge changes can be observed from the absorption spectra, but the absorption intensity presented a little change after the introduction of BaTiO₃. With the increase of the content of BaTiO₃, the photocatalytic performances of the composite samples increase and then decrease gradually with a best photocatalytic activity in the 10% TiO₂/BaTiO₃ composite sample.In the fourth chapter, we prepared TiO₂/graphene oxide composite materials by hydrothermal method. The composite samples were characterized by XRD, ultraviolet-visible absorption spectra, TEM and Raman spectrometer. The photocatalytic properties of the prepared samples were evaluated by photocatalytic degradation of MB solution. The XRD results showed that all the synthesized TiO₂ samples presented as the anatase phase. The absorption property of the samples after the introduction of graphene oxidedid not change significantly. TEM results showed that the lengths of TiO₂ nanotubes are mainly distributed in 100-200 nm. The outer and inner diameters of the nanotubes are 10-12 nm and 6-8 nm, respectively. Graphene oxide scattered in titanium dioxide nanotubes by lamellar structure. The best photocatalytic performance was presented in the composite sample coupled with 2 ml graphene oxide. Finally, we made a detailed analysis and discussions about the mechanisms about the photocatalytic performance variations after the introduction of graphene oxide.