Room Temperature Photocatalytic Oxidation of Carbon Monoxide Over Pd/TiO2–SiO2 Catalysts

The photocatalytic oxidation of carbon monoxide over TiO2–SiO2 and Pd/TiO2–SiO2 catalysts was studied. The catalyst samples were synthesized by using sol–gel technique coupled with hydrothermal treatment and all samples were hydrothermally treated before calcination in air. The catalyst samples were characterized by XRD, BET and DRIFTS techniques. The photocatalytic activity of the samples was determined by using circulated batch photoreactor coupled with in line gas transmission FTIR cell charged with 2,000 ppm carbon monoxide in air initially over 0.5 g of catalyst sample under 33 W (254 nm) irradiation power. XRD and BET results confirmed the presence of anatase phase and the decrease on the crystallite size of TiO2 with SiO2 addition which yield higher surface area and better dispersion of TiO2 over mesoporous SiO2. DRIFTS results indicated the presence of surface hydroxyls coordinated to Ti4+ and Si–O–Ti sites. All samples containing 10–90 % TiO2 over SiO2 exhibited significant photo oxidation activity at room temperature. The photocatalytic oxidation rate of carbon monoxide is favored by SiO2 addition due to high surface area, better dispersion of TiO2 particles and higher surface defects. The addition of PdO improves the photocatalytic activity significantly and the synergy between the TiO2 and PdO phases.