Theoretical Studies On The Mechanism Of Co Catalytic Oxidation On Au Surfaces

CO oxidation reaction is a relatively simple bimolecular reaction on the surface. Many industrial reaction processes involves the catalytic oxidation of CO, such as low-temperature water-gas shift, fuel cell reaction, CO oxidation catalysts, which is one of its elementary reactions. In the catalytic CO oxidation catalyst in the many, Au catalysts showed good performance of the catalytic oxidation of CO, not only has excellent low-temperature catalytic oxidation of CO at room temperature or activity, but also in wet conditions, activity is not reduced, even has been enhanced. At the same time, both in low or high concentrations have a good catalytic activity. Therefore, the study CO on metal surfaces on the physical and chemical behavior of the catalyst for the development and design has important practical significanceIn this paper, density functional theory and slab model were comprehensionly used to study catalytic oxidation reaction on the Au surfaces, the main findings are:(1) The best adsorption site was the top for CO on the steped surface Au (111) and open the surface of Au (100) . Adsorbed on the different surface has different energy barrier, as follows, Au (100)> Au (111), we also can find CO on Au (111) surface oxidation easier.(2) CO adsorbed on the Au surface stability, the most stable in the CO adsorption structures, CO adsorption on the surface are mainly two ways to achieve, namely: CO of 5σand the Au surface of the 6s,6pz,5dz2normal mixture, CO of 1Ï€and 2Ï€and the Au surface 5dyz,5dxz mixed. Among them, the latter achieved the CO of 2Ï€from the surface of the track to the electronic feedback, which to some extent, weakened CO bond.(3) CO at the Au surface of the reaction mechanism: CO + Oâ†'CO₂ and CO + O₂â†'OCOOâ†'CO₂ + Oâ†'CO + Oâ†'CO₂; while the Au (111) surface reaction mechanism of the reaction H₂O ,by CO + O + H₂Oâ†'CO + 2OHâ†'COOH + OHâ†'CO₂ + H₂O.(4) On Au (111) surface, there is H₂O system, CO oxidation reaction was had a certain influence, H₂O can make that CO can easily be oxidized, so H₂O in the reaction plays catalysis, and the reaction is generated O atom of CO₂ a part of from H₂O ,another partly of from O, that the experimental result is the same.(5) The CO on the O₂/PdAu (100) surface, by O₂ on the PdAu alloy can be decomposed into O atoms, the CO by the surface reaction mechanism of CO + Oâ†'CO₂ to provide the O atom, according to mechanism of CO + O₂â†'OCOOâ†'CO₂ + Oâ†'CO + Oâ†'CO₂ in progress, CO + O₂â†'OCOO reaction barrier is higher, is the reaction rate control step.