Photodegradation of toluene over TiO2-xNx under visible light irradiation

We report the photooxidation of toluene over nitrogen doped TiO2 (TiO2-xNx) under visible light irradiation. The photocatalytic oxidation of toluene in air over TiO2-xNx powders was studied using diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS), gas chromatography (GC), ion chromatography (IC), and gas chromatography mass spectrometry (GC-MS), focusing on the photocatalytic decomposition processes of toluene. Results obtained indicate that toluene, weakly adsorbed on the catalyst surface, is initially photooxidized to benzaldehyde which adsorbs onto the TiO2-xNx surface more strongly, leading to the formation of ring-opening products such as carboxylic acids and aldehydes. No gaseous intermediates were detected during the photooxidation. Major intermediates adsorbed at the catalyst surface were oxalic acid, ( COOH) 2, acetic acid, CH3COOH, formic acid, HCOOH, and pyruvic acid, CH3COCOOH, whereas more complicated carboxylic species, including propionic acid, CH3CH2COOH, isovaleric acid, (CH3)(2)CHCH2COOH, and succinic acid, (CH2COOH)(2), were also found in the early stage of the photooxidation. These intermediate products were gradually photodegraded to CO2 and H2O under visible light irradiation.