Of Tio <sub> 2 </ Sub> Core-shell Materials Preparation, Structure And Properties

In the 21st century, the human being benefits from the rapid development of science and technology, at the same time we also face the challenge of energy crisis, environmental degradation. How to solve the problems is all circles of the society especially the scientific researchers` historical mission. It is urgent to develop green functional materials which can utilize energy sources effectively.Titanium dioxide is one of environmental friendly materials. The research of titanium dioxide is closely related with the environment and energy. Nano-scale titanium dioxide has been widely investigated because of its lots of merits, such as strong oxidizing power, chemical stability, high photocatalytic avtivity, non-toxicity, low cost. Titanium dioxide core-shell materials have received more and more attention due to their large specific surface area, high photocatalytic properties. In this dissertation, explorations have been carried out on the synthesis of titanium dioxide microspheres and study of their photocatalytic properties. The main achievements could be summarized as follows:Firstly, monodisperse polystyrene microspheres were prepared by polymerization method, and then titanium dioxide microspheres were synthesized by hydrolysis of titanium butoxide by using polystyrene microspheres as templates. Titanium dioxide hollow spheres were further obtained under 500℃calcined. SEM micrograph results show that the diameter of the titanium dioxide hollow spheres are about 700⁸00nm, and the XRD results show that titanium dioxide hollow spheres have the characteristic peaks of anatase phase without any impurity peak corresponding to rutile phase. The photocatalytic performance for hydrogen production of TiO₂ microspheres is higher than that of P25.The TiO₂@Ag core-shell materials were obtained by the hydrazine reduction of Ag+ ions on the surface of the TiO₂ microspheres in AgNO3 solution. The absorptions of TiO₂@Ag core-shell materials at visible range are enhanced obviously because of surface plasmon effect, which further enhance the photocatalytic activity of the corresponding TiO₂ microspheres. It is found that the as-prepared TiO₂@Ag core-shell material with the nominal mol ratio as 0.9 (silver to titanium dioxide) has the highest photocatalytic activity.The prepared TiO₂ core-shell materials were also used as photoelectrode materials in Dye-sensitized solar cells(DSSCs). In our study, the photoelectrode has a special double-layer structure. The bottom layer of the photoelectrode is fabricated by TiO₂ nano-particles which were synthesized by hydrothermal method. The top layer of the photoelectrode has a porous structure which was made by the mixture of TiO₂ core-shell materials and TiO₂ nano-particles. The XRD results indicate that the titanium dioxide in the photoelectrode has the characteristic peaks of anatase and rutile phase. When the titanium dioxide was doped by a certain amount of Ag, the relative content of rutile phase decreased, which indicate that the conversion of TiO₂ from anatase to rutile phase can be prevented by a certain amount of Ag doping. The proportion of Ag in the photoelectrode which calculated from XPS results is consistent with that of the experiment. It can be seen from the I-V curves that the conversion efficiencies of the corresponding DSSCs are enhanced with increasing the content of Ag in the photoelectrodes.