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A carbon nanotubes (CNT)/TiO 2 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/TiO 2 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 TiO 2 . One is to act as an electron reservoir, which helps to trap electrons emitted from TiO 2 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 TiO 2 particles in the CNT/TiO 2 nanocomposite, and this important role was neglected in previous studies. Accordingly, a reasonable model is proposed to expain the role of CNT in CNT/TiO 2 composites as a photocatalyst for degradation of organic pollutants.
Xu et al. (2010) studied this question.