Study about enhancement photocatalytic ability of TiO2 and Black TiO2 via nanocomposite with diverse metal

Abstract

Titanium dioxide (TiO2) existed as three forms as anatase, rutile and brookite has a large oxidation and reduction power and is commonly known as a photocatalyst, absorbing the wavelength of ultraviolet region to activate catalytic activity. The main light source used in photocatalytic industrialization is commonly the sunbeam but the portion of ultraviolet light in the sunlight is only 5 %. TiO2 as photocatalyst is able to produce a sufficient photocatalytic efficiency only with a little of ultraviolet but the limitation, small portion of ultraviolet in sun light, is the challenge in the Titania study considering practical amount of solar power reaching to the earth. Therefore, TiO2-metal composite was prepared to verify and improve the photocatalytic activity by lowering the bandgap energy and utilizing in the range of the ultraviolet ray and even in the visible light as well. Furthermore, the effect of not only TiO2 nanoparticles but also TiO2 nanofibers is expected by increasing the photocatalytic efficiency contrasted with the same area and volume. The TiO2 nanoparticle and TiO2 nanocomposite with metal oxide were synthesized using sol-gel method. The characteristics such as structure properties and bandgap energy were analyzed through X-ray diffraction and calculate UV-Vis spectrometry. To control size of Titania, the nanoparticle synthesized by using CTAB surfactant was obtained the lowest size, 12.68 nm in pH 7, among each sample by diverse pH and using PEG surfactant was 41.65 nm in pH 7. Moreover, the experimental to decrease the band gap energy by adding metal oxide into Titania was conducted so TiO2 nanocomposite with iron oxide had a band gap energy of 1.60 eV, which was exhibited the lowest energy value among the four other samples (TiO2Ag/TiO2, V/TiO2, Ni/TiO2). The black TiO2 nanoparticle was obtained by reducing the surface of common TiO2 through calcination step under a hydrogen atmosphere. The hydrogen treated TiO2 nanoparticles to have a lower band gap as 0.3 eV – 0.9 eV than the conventional TiO2 nanoparticle. Titania nanofibers were prepared by electrospinning equipment. The photocatalytic properties were obtained through methylene blue decomposition test with nanofiber optimized as thin and successive. The optimization condition, 9 wt % polymer, 15 kV applied voltage, and the ratio of precursor and solvent (2:14), made nanofiber structure be stabilized. Nanofibers with metal oxides were also synthesized under optimum conditions and the photocatalytic property was conducted by methylene blue decomposition experiments. Fe/TiO2 nanofiber calcined at 450 ℃ was found as enhanced decomposition efficiency (C/C0 = 0.109) comparing with TiO2 nanofiber decomposition efficiency (C/C0 = 0.283). The black TiO2 nanofiber was also manufactured under the H2 gas when the TiO2 nanofiber was calcined. Methylene blue degradation was carried out and got a similar result with general TiO2 fiber. According to these results, TiO2 synthesized in this thesis is able to be utilized as sensor and electronic material, with the photocatalytic properties activating even in less energy.