Theoretical Study on Mechanism of CO Oxidation Catalyzed by Ag2-

The mechanism of Ag-2(-)-catalyzed CO oxidation was investigated at the level of B3LYP theory. The computational results indicate that the absorption energy of O-2 on Ag-2(-) is close to that of O-2 on Au-2(-), while the absorption of CO on Ag-2(-) is stronger than that of CO on Au-2(-). There are four reaction pathways for CO oxidation catalyzed by Ag-2(-). The most feasible pathway is the CO insertion into the Ag-O bond of Ag2O2- to produce an intermediate [Ag-AgC(O-O)O](-), and then the intermediate [Ag-AgC(O-O)O](-) decomposes into product CO2 and Ag2O-, or another CO molecule attacks [Ag-AgC(O-O)O](-) to form two CO2 molecules and Ag-2(-) anion. The most difficult pathway is the di-silver carbonate intermediate pathway, which needs to overcome a total energy barrier of about 0.24 eV. Since for gold, the carbonate-like intermediate pathway requires an activation barrier of 0.61 eV, silver proves to be a better catalyst than gold.