| TiO2, a multi-functional semiconductor material, is applied in optoelectronic fields since it is non-toxic, stable and wildly abundant. But the limitations such as wide band gap, low surface area and surface defects affect its performances. Many strategies have been proposed for optimizing photoelectric performance of TiO2, with fine control of its morphology being one of the most effective. Hollow sphere materials possess good light scattering, larger surface area and tunable morphology, showing good performance in applications. Besides, numerous investigations reported that the addition of noble metals including gold and platinum is also an effective way to enhance the photoelectric performance. Due to high Schottky barrier between metal and TiO2, it not only eliminates the recombination of electrons and holes by increasing the charge separation, but also extends the wavelength range response by photosensitization. In this thesis, Au/Pt doped TiO2 hollow spheres which integrate superiorities of hollow spheres structures and noble metal were prepared and the related photoelectric properties of the materials were investigated.A novel TiO2 hollow microsphere was synthesized by solvethermal method, following by depositing controllable nano-Au through an effective and facile in situ reduction approach to obtain TiO2/Au composites. The effect of nano-Au on TiO2's photoelectric performance was evaluated by the degradation of methylene blue (MB) under UV or visible light irradiation. It was found that the Au doped TiO2 hollow spheres show excellent photocatalytic properties and extend the light absorption spectrum into the visible region. TiO2/Au composites exhibit the fastest degradation rate of MB when the weight percent of the deposited Au nanoparticles is 2.8 wt%. Furthermore, the TiO2/Au (Au,2.8 wt%) catalyst exhibits MB removals of 99.77% under UV irradiation and 84.25% under visible light irradiation after 150 min reaction.To avoid noble metal loss and incident light loss with noble metal depositing on the surface, anatase Au@TiO2 core-shell materials were prepared with Au@SiO2 template and an additional SiO2 outer protecting layer. The Au@TiO2 materials act different morphologies, structures, crystallinities and porosities after calcinations at 500?and 800? respectively. And the photoelectric performances of Au@TiO2 were investigated by MB degradation and dye-sensitized solar cell (DSSC). Au@TiO2 treated with 500 ? sintering shows good absorption ability in 17.61 mg/L MB solution and dye removals of 77.27% within 30 min in the dark. The excellent performance depends on its large surface area (77.36 m2/g) which benefits from fibrous structure. Au@TiO2 treated with 800 ? sintering have good absorption capacity as well as photocatalytic activity as its improved crystallinity (absolutely anatase). In addition, a bilayer anode of DSSC was fabricated with Au@TiO2 and P25 film on FTO glass.The photocurrent and photoelectric conversion efficiency of bilayer DSSC were 13.12%,9.34% enhancement respectively, compared to P25 single layer which lack of light scattering effect produced by Au@TiO2 hollow spheres.Due to photoelectron loss caused by the disorder of Au@TiO2 hollow spheres mentioned above, three-diamensional (3D) ordered macroporous M@TiO2 hollow spheres films were directly prepared on ITO glass using size and component controllable M@RF microspheres as template and their photoelectric performance was investigated. The ordered hollow spheres connect with each other through cavity in the shell which provides effective channel for photoelectrons. Au and Pt have different influence on the photo-detective performance. Au-doped 3D-ordered TiO2 show a high responsivity (1561.25 A/W) to UV light (365 nm), but it has long response time and larger off photocurrent, while Pt-doped 3D-ordered TiO2 show rapid response speed, low responsivity and very low dark current. The rising time of Pt-doped TiO2 is 14.6 s and the dark current is only 1.913 nA at a 1.0 V bias. Compared to only Au doped or Pt doped, AuPt alloy doped 3D-ordered TiO2 materials balance responsivity and response time. It has meet the requirements of practical application with shorter light current rising time 17.5 s, higher responsivity 2.14 A/W and lower dark current 22 nA. |
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