Uniform carbon-covered titania and its photocatalytic property

A series of carbon-covered titania (CCT) were prepared via pyrolysis of sucrose highly dispersed on the surface of titania in flowing N-2. The samples were characterized by XRD, BET, DTA-TG, UV-vis, and their photocatalytic properties were evaluated with a model pollutant, methylene blue (MB), at room temperature. It is found that carbon coverage inhibits the phase transformation of TiO2 and makes the absorption edge of titania shift to the visible region. Photocatalytic tests show that under UV illumination, the kinetics of the dyes' elimination in the suspension of CCT powders follows an apparent first-order rate as in pure titania suspension, but the rate constant is much higher than that of pure titania, even commercial Degussa P-25 TiO2. In addition, as a photocatalyst responsive to visible light, CCT shows similar kinetic features for the photodegradation of the dyes under visible light illumination to that under UV illumination. From the detection of the products of MB degradation, and the absorption spectra of MB solution after the photocatalytic reaction, it is proved that MB is decomposed over CCT samples under visible light illumination, whereas it is simply bleached over pure titania at the same condition. (c) 2005 Elsevier B.V. All rights reserved.