Photocatalytic degradation of volatile organic compounds at the gas-solid interface of a TiO₂ photocatalyst

In the present work, photocatalytic degradation of volatile organic compounds including gas-phase trichloroethylene (TCE), acetone, methanol and toluene over illuminated TiO₂ was closely examined in a batch photoreactor as a function of water vapor, molecular oxygen and reaction temperature. Water vapor enhanced the photocatalytic degradation rate of toluene, but was inhibitive for acetone, and, there was an optimum water vapor concentration in the TCE and methanol removal. In a nitrogen atmosphere, it showed lower photocatalytic degradation rate than in air and pure oxygen. Thus, it could be concluded that oxygen is an essential component in photocatalytic reactions by trapping photogenerated electrons on the semiconductor surface and by decreasing the recombination of electrons and holes. As for the influence of reaction temperature, it was found that photocatalytic degradation was more effective at a moderate temperature than at an elevated temperature for each compound.