Preparation of Carbon-Nanotube-supported TiO2 for Enhanced Dye-degrading Photocatalytic Activity

Titanium dioxide-carbon nanotube (TiO2-CNT) nanocomposites were successfully synthesized by a sol-gel method. The prepared TiO2-CNT samples were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The photocatalytic activity of the samples was tested by photodegradation of methylene blue (MB) and methyl orange (MO) in aqueous solution under UV-light irradiation. In the photocatalytic results, the TiO2-CNTs, as compared to the pristine TiO2 and commercial P25 TiO2 photocatalysts, exhibited the fastest degradation performance in both dye solutions. The TiO2-CNTs' apparent rate constants were 0.0232 and 0.0214 min(-1) in the MB and MO solutions, respectively, both of which are approximately 5 times greater than that for the commercial P25 TiO2 (MB: 0.0046 min(-1), MO: 0.0043 min(-1)). And as for the estimated electron-transfer resistance (R-ct) results from the ac impedance spectra, the values increased in the following order: TiO2-CNT < P25 TiO2 < pristine TiO2, indicating that CNTs can serve as electron-transmitting paths, thus suppressing the recombination rate of photogenerated electron/hole pairs. Moreover, the degree of photodegradation inhibition was insignificant in the presence of interfering anion species (1000-fold).