New Insight for Enhanced Photocatalytic Activity of TiO₂ by Doping Carbon Nanotubes: A Case Study on Degradation of Benzene and Methyl Orange

Abstract

A carbon nanotubes (CNT)/TiO2 nanocomposite photocatalyst has been prepared by a simple impregnation method, which is used, for the first time, for gas-phase degradation of benzene. It is found that the as-prepared CNT/TiO2 nanocomposite exhibits an enhanced photocatalytic activity for benzene degradation, as compared with that over commerical titania (Degussa P25). A similar phenomenon has also been found for liquid-phase degradation of methyl orange. The characterization of photocatalysts by a series of joint techniques, including X-ray diffraction, transmission electron microscopy, ultraviolet/visible (UV/vis) diffuse reflectance spectra, and photoluminescence spectra, discloses that CNT has two kinds of crucial roles in enhancement of photocatalytic activity of TiO2. One is to act as an electron reservoir, which helps to trap electrons emitted from TiO2 particles due to irradiation by UV light, therefore hindering electron−hole pairs recombination. The other is to act as a dispersing template or support to control the morphology of TiO2 particles in the CNT/TiO2 nanocomposite, and this important role was neglected in previous studies. Accordingly, a reasonable model is proposed to expain the role of CNT in CNT/TiO2 composites as a photocatalyst for degradation of organic pollutants.