Abstract
In my study, various titanium-oxide related materials were obtained from reacting TTIP with formic acid or acetic acid by solvothermal method. In the case of acetic acid, three kinds of product were synthesized, which are fibrillar titanate (FT), chrysanthemum-like titanate (CT) and elliptic anatase TiO2 (ET). Both FT and CT are the new titanates which have acetic acid and acetate intercalated in the layers of their crystal structure. The intercalated organic species were confirmed by FTIR and TGA-MS spectra, and can be carbonized to form the uniform carbon networks at the temperatures over 350 oC. Additionally, CT can be converted to TiO2-B and anatase by calcinations. Hence, C/TiO2 composites with anatase and TiO2-B can be acquired after the carbonization of CT. The C/TiO2 composites were used as the active material of the anode of Li-ion battery and showed excellent performance (145 mAh/g at 10C rate). CT800 is the material obtained by annealing CT at 800 oC for 1 hour. After annealing, the crystal structure can be converted to anatase TiO2 completely, and was utilized in photocatalyst application. Interestingly, CT800 exhibited higher photoactivity than the commercial TiO2 (P25), the k value of CT800 was 1.4 times higher than P25. In order to discover the key factors that governed the photocatalytic properties, the specific reduction of Ag+ ions was carried out and EPR spectra of CT800 were obtained. Both an HADDF image and EDX mapping indicated that the Ag+ ions tended to be reduced close to the center of the micro matrix of CT800. Moreover, the EPR spectra strongly suggest that the excited electrons tended to migrate toward the center of the micro matrix, resulting from a multiple junction, “cascade effect”, which efficiently reduces the recombination of excited electrons and holes and greatly increases the photoactivity. Additionally, the special morphology of CT800 was responsible for not only multi-scattering around 350 nm, which strongly enhancing the harvesting of light, but also the hot spots at the surface of nano sheets and then contributing to its outstanding photocatalytic activity. Otherwise, in the case of formic acid, as the reaction takes place at low temperature, the rod-like titanate was formed initially and showed poor crystallinity. Once elongating the reaction time at the same temperature, the hydrangea-like titanate appeared and exhibited better crystallinity. These results are similar to the observations of our previous study that the reaction was taken place by sol-gel method using reflux system. When the temperature was arisen, the {101} exposed octahedron TiO2 was observed and was assigned to anatase TiO2 by TEM and XRD. Once the 0.1 M fluorine was contained in the solvents, fluorine bonded to the five-coordinated Ti atoms of the {001} surface and limited the crystal growth along <001>. Hence, the plate-like TiO2 was obtained at 150 oC. Moreover, the thickness of the particle decreased dramatically as the concentration of fluorine increased to 0.2 M. The particles aggregated and became flower-like TiO2, which was also exposed {001} facets. The flower-like TiO2 which is constructed by many ultra-thin nano sheets may have the potential to be used as the active material of the anode of Li-ion battery due to the dramatically decreased in length for Li-ion to intercalate into the material. Furthermore, the photoactivity of these materials could be discovered in the future.