Synthesis of CNT-titania-silica nanocomposite thin films: the effect of heat treatment on photocatalytic activity

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2014
Kırbaş, Tuğçe
In this study, CNT-TiO2-SiO2 nanocomposites were synthesized by sol-gel process and the thin films over glass substrates were fabricated by dip coating method. The effects of CNT addition, heat treatment temperature and atmospheres on the structure and photocatalytic properties were examined. The thin films were prepared with and without carbon nanotubes and the heat treatment was carried out at different temperatures in the range of 300-600oC under air and nitrogen atmosphere. Characterization of the samples was performed by thermal analysis, XRD, SEM&EDS, elemental carbon analysis, XPS and UV-Vis spectroscopy. Thermal analysis indicated that the oxidation temperature of carbon nanotubes was reduced significantly by the presence of TiO2-SiO2 and considerable amount of carbon is oxidized under nitrogen atmosphere. XRD studies showed that the crystallinity is enhanced by heat treatment temperature. The SEM images revealed that CNTs were successfully incorporated in thin film structure. Elemental carbon analysis was performed to obtain the residual carbon amount after heat treatment. The results were consistent with thermal analysis and showed that quantity of carbon is decreasing with increasing temperature under both air and nitrogen atmospheres. UV-Vis Spectroscopy indicated the photoabsorption edge of thin films is at UV region which is in agreement with titania. XPS studies showed that the reduction of Ti4+ to Ti3+ sites during heat treatment under nitrogen flow and these oxygen vacancies over the surface are known as effective sites for photocatalysis. The photocatalytic activity tests were performed by monitoring the degradation of metyhylene blue under UV irradiation in the presence of the thin film. The CNT-added samples have higher photocatalytic activity than the TiO2-SiO2 sample. And also higher heat treatment temperatures favor the photocatalytic activity until the sintering. The most photocatalycally active sample is found as the CNT-TiO2-SiO2 thin film that was heat treated at 500oC under air atmosphere.

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Citation Formats
T. Kırbaş, “Synthesis of CNT-titania-silica nanocomposite thin films: the effect of heat treatment on photocatalytic activity,” M.S. - Master of Science, Middle East Technical University, 2014.