GAS PHASE OXIDATION OF FORMALDEHYDE BY TIO2/TIO2-V2O5/POLYPYRROLE ENERGY STORAGE PHOTOCATALYST

Abstract

Photocatalytic oxidation of formaldehyde was performed through an electron storage photocatalyst named TiO2/TiO2-V2O5/PPy nanocomposites, consisting of TiO2 responsible for an electron generating source, TiO2-V2O5 functional as an electron storage substance, and PPy (polypyrrole) as an electron conducting substance between the formers. It was found that the TiO2/TiO2-V2O5/PPy nanocomposites showed both adsorption and photocatalytic activity for formaldehyde removal. Under UV irradiation, the catalytic activity of the TiO2/TiO2-V2O5/PPy catalyst was 57%, which was 0.1 and 0.4 times higher than that of TiO2 and TiO2/PPy catalysts, respectively. Moreover, the TiO2/TiO2-V2O5/PPy catalyst retained its function for at least 3 hours, after UV irradiation for 3.5 hours. The presence of TiO2-V2O5 was found to enhance the photocatalytic activity of the TiO2 catalyst, including the ability to function in the absence of UV light. This is due to the lower energy band gap of the TiO2/TiO2-V2O5/PPy, compared to that of TiO2; the TiO2-V2O5 also possesses energy storage ability. Further, the reaction rate of photocatalytic oxidation of formaldehyde by the electron storage photocatalyst was determined. The formaldehyde destruction rate is a function of formaldehyde concentration and can be formulated using a simplified Langmuir-Hinshelwood.