Synthesis And Its Photocatalytic Activity Of Carbon-modified-TiO₂ Hybrid

Environment pollution was more serious with the increasing of industrial and domestic waste and threatened to the human heath. Titanium dioxide is the most promising semiconductor photocatalytic material for the degradation of environmental organic pollution due to the properties of efficient, non-toxic and no secondary pollution. However, the band gap energy (3.2eV) of the anatase TiO2 is the major drawback for its practical application, since the reaction can only be initiated under UV irradiation (which is only approximately 4% of solar radiation) and the photogenerated electron/hole is prone to recombination. Therefore, the modification on TiO2 towards an efficient visible light-induced photoactivity has been the major research effort. In our study, the carbon-based (DWCNT、C70、C60+70) TiO2 hybrids were prepared by hydrothermal method and characterized. The photocatalytic activity of carbon-based TiO2 hybrids was tested by the photocatalytic degradation of sulfathiazole. The detail researches and conclusions are as follows:1) Double-walled carbon nanotubes (DWCNT)-TiO2 hybrid was prepared by hydrothermal method and characterized by X-ray diffraction, electron microscopy, N2-adsorption analysis, Raman spectroscopy, Fourier transform Infrared spectroscopy, and UV-vis diffuse reflectance spectroscopy. The photocatalytic activity of DWCNT-TiO2 hybrid and the effect of the length of tube were tested by the photocatalytic degradation of sulfathiazole. The experimental results showed that the DWCNTs were evenly coated with TiO2 nanoparticles which generated an intimate contact between the DWCNTs and TiO2. The introduction of the DWCNTs provides DWCNT-TiO2 hybrid with visible light-induced photoactivity and a large surface area, and prolongs the lifetime of photogenerated electron/hole. Meanwhile it can decrease the grain size of anatase TiO2 which can enhance the photocatalytic activity. The DWCNT-TiO2 hybrid showed an excellent visible-light-induced activity, compared with multi-walled carbon nanotube-TiO2 and single-walled carbon nanotube-TiO2 hybrids, which can be attributed to the unique electronic structure of the DWCNTs that can worked well as not only a photosensitizer but also an electron conductor. In addition, DWCNT-TiO2 hybrid with the DWCNTs of long length showed higher degradation efficiency than that with the short length.2.5 wt.% DWCNT-TiO2 has the best photocatalytic activity.2) C70-TiO2 hybrid was prepared by a hydrothermal method using titanium sulfate as the precursor and characterized by UV-Vis diffuse reflectance spectroscopy, Fourier transform Infrared spectroscopy, Raman spectropy, transmission electron microscope, scanning electron microscope, X-ray diffraction, BET, fluorescence spectrometer and X-ray photoelectron spectroscopy. The results indicated that there is an intimate contact between the C70 and TiO2 via covalent bonding and the introduction of C70 can promote the survival time of photos.TiO2 modified by C70 was provided with visible light induced photoactivity. The grain size of anatase TiO2 was decrease with the increase of the content of C70, and then the photogenerated electron/hole can migrate into the surface of TiO2 quickly. The photocatalytic activity of C70-TiO2 was estimated by the degradation of sulfathiazole under the visible light irradiation. The nanocomposites demonstrated an excellent visible light induced activity compared with the pure TiO2 and C60-TiO2, which was due to the higher two-photo cross-sectional area and better electron affinity.18 wt.% C70-TiO2 showed the greatest photocatalytic activity and the repeatability of photocatalyst was excellent.3) C60+70-TiO2 hybrid was prepared by a hydrothermal method using titanium sulfate as the precursor and characterized by UV-Vis diffuse reflectance spectroscopy, Fourier transform Infrared spectroscopy, Raman spectropy, transmission electron microscope, X-ray diffraction, BET, fluorescence spectrometer and X-ray photoelectron spectroscopy. The results indicated that there is an intimate contact between the C70 and TiO2 via covalent bonding and the introduction of C70 can decrease the grain size of anatase TiO2 and then the photogenerated electron/hole can migrate into the surface of TiO2 quickly.TiO2 modified by C70 was provided with visible light induced photoactivity.. The photocatalytic activity of C60+70-TiO2 was estimated by the degradation of sulfathiazole under the visible light irradiation. The nanocomposites demonstrated an excellent visible light induced activity compared with the pure TiO2 and C60-TiO2, but inferior to the C70-Ti02.12 wt.% C60+70-TiO2 showed the prominent photocatalytic activity and the repeatability of photocatalyst was excellent.4) Comparing the above three types of carbon-modified-TiO2 hybrid, the results dispalyed that 18 wt.% C70-TiO2 nanocomposites had the best optical and electronic characteristics, and the highest visible light photocatalytic activity.Carbon-modified-TiO2 hybrid synthesized via hydrothermal method had better visible light photocatalytic activity. The study provides a new way for the modified TiO2 and has important theoretical significance and practical value.