Preparation, characterization and visible-light activity of carbon modified TiO₂ with two kinds of carbonaceous species

Visible-light responsive carbon modified TiO₂ was synthesized through simple precipitation of tetrabutyl titanate in proper amount of water. The as-synthesized catalyst was characterized by elemental analysis, N₂ adsorption-desorption analysis, X-ray powder diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectra (DRS) and nuclear magnetic resonance (NMR). The results indicate that carbon modifies TiO₂ in two ways: doping as interstitial carbon in the crystal lattice and coating as graphite-like carbon on the surface. It is found that the interstitial carbon could narrow the band gap, and the graphite-like carbon could serve as sensitizer. The sensitization effect of graphite-like carbon is found to contribute greatly to the excellent photocatalytic performance of carbon modified TiO₂. It has been found that 95.6% of MO was decolorized within 120 min and 92.7% of Cr(VI) was reduced within 90 min in the presence of phenol. The formation mechanism of the carbon modified TiO₂ has been discussed.