The Elimination Of CO In The Environment By Photocatalytic Oxidation

The catalytic oxidation of CO with 02 is one of the simplest bimolecular surface reactions which can be used as a model for the research of the photocatalytic-oxidation reaction mechanism. CO is also one of the hazardous pollutants and its elimination from the environment is of great importance. So the study of CO catalytic oxidation possesses theoretical and practical interest.The photocatalytic-oxidation of CO on the xidized?hO2 and Pd(2wt%)ITiO2(oxidized) were investigated at room temperature , it was found that there are two effects (wavelength effect and photo-enhancement effect ) which did not be reported in literature yet. The influence of water vapor on CO photocatalyticoxidation was also studied. X-ray powder diffraction (XRD) , X-ray photoelectron spectroscopy (XPS), transimission electron microscope (TEM) and BET method were used to characterize the catalysts.On the xidized?Ti02 no CO photooxidation reaction was observed with 4W black light lamp( X =365 nm) radiation, but CO photocatalytic-oxidation could be carried out with 4W bacterical lamp( A 254 nm) radiation at room temperature. Refening to the catalytic oxidation mechanism of CO on transition metals, it was explained by: O2(a) obtained by the ionsorption of 02 on the xidized?TiO2 could not oxidize CO, CO photooxidation reaction only occurred when O(~) was produced under 4W bacterical lamp (X =254 nm) illumination. The reaction mechanism is as follows:The photo-enhancement of CO oxidation reaction on Pd(2wt%)/Ti02(oxidized) was investigated. It was found that the CO oxidation activity of Pd(2wt%)/Ti02(oxidized) is greatly enhanced if illuminated with 4W black light lamp( A =365mn) and 4W bacterical lamp( A =254nm) as compared with that in the dark at room temperature. A, mutual enhancement model of heterogeneous photo-dark catalysis for CO oxidation was proposed to elucidate this phenomenon. The reaction mechanism is as follows:The influence of water vapor on CO photocatalytic-oxidation on the 搊xidized擳i02 and Pd(2wt%)ITiO2(oxidized) were also investigated at the room temperature. It was found that the reaction rate of CO oxidation on the 搊xidized?hO, by bacterical lamp illumination and on Pd(2wt%)/TiO2(oxidized) by both black light lamp and bacterical lamp illumination are dramatically decreased when the raw gas is saturated with 3.3 6kPa water vapor. We suggest that the OH radicals will be produced through the reaction of 1120 with O(a) or 0(a) on TiC)2 surface and Pd surface. 0H radicals can抰 oxide CO. The decrease of O(a) and O(a) concentrations on catalyst surface resulted in the decrease of the CO oxidation rate.