Study On The Effect Of Visible Light Irradiation On CO Oxidation Over Au Nanoparticles Supported TiO₂or Al₂O₃

The removal of CO is of great scientific and technological value in thepurification of air as well as the purification of H2in the development of efficientproton exchange membrane fuel cell (PEMFC) systems. The supported nano-nobelmetals catalyst at low temperature removal of CO and CO selective oxidation is oneof the most effective methods. However, due to the presence of both deactivation ofCO oxidation and low selectivity of CO oxidation in rich-H2stream over Au catalyst,how to improve the activity and stability of oxidizing CO at low temperature, andthe preferential oxidation of CO in the H2-rich streams over such catalysts hasalways been pursued.In this paper, Au/Al2O3and Au/TiO2catalysts have been prepared bydeposition-precipitation method. Based on the visible light absorption behavior ofAu nanoparticles induced by localized surface plasmon resonance (LSPR), a visiblelight is introduced to the reaction system of oxidizing CO and selectively oxidizingCO over supported Au catalysts, and the catalytic activities of the Au catalysts wereperformed for oxidizing CO in the absence and presence of H2, respectively. Thechemisorptive properties of CO, O2, H2and CO/H2mixed gas at the surface of Aucatalysts under visible light irradiation were investigated. Considered with theproperties of catalysts, e.g. the crystal structure, surface area, morphology, lightabsorption and surface chemical state, the reaction mechanism of oxidizing COunder visible light irradiation have been discussed.The following results and conclusions were obtained from these studies:(1) In the absence of H2, the introduction of visible light can significantly promotethe catalytic oxidation of CO on both Au/TiO2and Au/Al2O3catalysts, which theeffect on Au/TiO2is much larger than that on Au/Al2O3;(2) In the presence of H2,the introduction of visible light can improve the selective oxidation of CO overAu/TiO2catalyst;(3) For Au/Al2O3catalyst, the visible light irradiation can improvethe selective oxidation of CO in the presence of a less mount H2, but suppress theselective oxidation of CO in a H2-rich stream. Based on the chemisorption behaviorof reactants on the catalysts, it is proposed that the visible light irradiation canincrease the surface electron density of Au nanoparticles via the LSPR effect, which is benefited to the adsorption of CO and its activation at the surface of Aunanoparticles, and then the oxidation of CO. Moreover, the visible light irradiation isalso beneficial to the competitive adsorption of CO at the surface of Aunanoparticles in the presence of H2, resulting in the preferential oxidation of CO.The original results of this study are as follows:(1) Based on the property oflocalized surface plasmon resonance (LSPR) of Au nanoparticle, the visible lightwas firstly introduced to the reaction system of CO oxidation and selective oxidationof CO in H2-rich stream. This maybe develop a new feasible method to remove COin indoor and to purify H2steam in fuel cell systems;(2) This effect of visible lightirradiation may also be applied to other thermo-catalytic reaction system, whichmaybe provides a new approach to improve the thermo-catalytic activity.