Preparation And Photocatalytic Activities Of Yttrium Doped Titanium Dioxide Nanofibers

Semi-conductive catalysis has been widely used in air cleaning, water purification and antibacterial areas as a novel environment-friendly technology. Nano-titanium dioxide (nTiO2) is the most popular semi-conductive photo catalyst due to the high photochemical activity, bio-and chemo-inertness and anticorrosion behaviors. However, nTiO2is confronted with such limitations as low photon efficiency and photocatalytic activity due to the rapid combination of electrons and holes. In addition, the absorption band of nTiO2is located in ultraviolet region due to the wide forbidden band. Therefore, it is becoming a hot topic to exploit the ways to improve the photocatalytic activity of nTiO2and the application efficiency of visible light. Nanofibers gave good physical and chemical properties and high specific surface area, resulting in high surface energy and photocatalytic activity. In addition, the fibrous feature makes it quite easy to recover the catalysts from solutions and suspensions. In this thesis one dimensional TiO2naofibers were prepared by the use of electrospinning and sol-gel technologies. To achieve a better visible light catalytic activity, Y3+was adopted into the TiO2naofibers.TiO2sol-gel was obtained from butyl titanate as the precursor, ethanol as the solvent and ice acetic acid as the catalyst to ensure proper viscosity for electrospinning process. Polyvinyl pyrrolidone (PVP) fibers with entrapped TiO2and Y3+were prepared by blend electrospinning, followed by heat treatment to obtain Y3+adopted TiO2fibers. The morphology, structure and photo-absorption profiles were characterized by thermogravity-differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and ultraviolet-visible absorption spectroscope (UV-Vis). The obtained TiO2nanofibers indicated an average diameter of118±26nm, while that of Y3+-dopted TiO2fibers of147±18nm. The crystal size of TiO2became smaller with the increase in the amount of Y3+doped. A red shift of absorption band was found after Y3+doping, resulting in apparent absorption in visible region.The photocatalytic performance of TiO2nanofibers and Y3+adopted TiO2nanofibers was determined on methyl orange under irradiation of a daylight lamp. The most significant degradation of methyl orange was found on TiO2fibers doped by1.5%Y3+and heat-treated at550℃. Around90.6%of methyl orange degradation was detected after4h irradiation and the degradation rates were maintained over80%after repeat uses for5times. The photocatalytic dynamic study showed the degradation mechanism of Y3+-doped TiO2nanofibers under visible region followed an L-H first order model.