Carbon-doped TiO2 film to enhance visible and UV light photocatalytic degradation of indoor environment volatile organic compounds

Carbon-doped P25, a visible-light-driven photocatalyst, was prepared to remove methyl ethyl ketone (MEK) from the indoor air environment. The effect of key parameters such as carbon content, relative humidity and light type on the photocatalyst efficiency, reaction rate and by-products generation rate were evaluated. C-doped P25 photocatalysts coated on nickel foam enhanced photocatalytic degradation and the reaction rate of gas-phase MEK under visible and UV light, compared with a commercial P25 coated on the same substrate material. The results indicate that the photocatalytic degradation efficiency and the reaction rate of all examined photocatalysts under UV light are higher than visible light. All the experiments were carried out in two continuous reactors with a small residence time (0.025 s), 2.95 mg/m(3) (1000 ppb) inlet contaminant concentration and at four different relative humidity levels (0, 20, 40 and 60 %). As a result, the optimum relative humidity was 20 % and 40 % for visible-PCO and UV-PCO of C-doped P25, respectively. Moreover, C-P25-0.1 % showed the highest MEK degradation under all tested conditions. The removal efficiency was enhanced from 77 % to 94 %, when three layers C-P25-0.1 % photocatalyst, was under UV light, and increased from 50 % to 67 % under visible light. Moreover, the by-product generation was considerably decreased for three-layer C-P25-0.1 % photocatalyst.