Carbon-coated TiO₂ composites for the photocatalytic degradation of low concentration benzene

Carbon-coated TiO₂ was synthesized by mixing TiO₂ powders and polyethylene glycol, followed by heat treatment in nitrogen atmosphere. All samples were characterized by powder X-ray diffraction, UV diffuse reflectance spectroscopy, high-resolution transmission electron microscopy, and nitrogen adsorption. The photocatalytic activity of carbon-coated TiO₂ for benzene degradation was investigated with a benzene concentration of ~1.2×10^-5. Results showed that the residual carbon content was influenced greatly by heat treatment temperature (HTT) and the amount of PEG, which decreased and increased with increasing the temperature and the amount of PEG, respectively. The crystallinity of TiO₂ was improved when the HTT increased. However, the carbon residue had an inhibition effect on the crystal growth of TiO₂. The carbon-coated anatase samples were shown to exhibit higher photocatalytic activities than the pristine TiO₂ because of the adsorption enrichment of benzene by carbon around the anatase particles and of the effective charge separation due to the electronic conduction of carbon. Another important factor affecting photocatalytic activity was the crystallinity of the anatase phase. High photocatalytic activity for benzene requires a balance between the carbon content and the anatase crystalline structure.