CO Oxidation by Molecular and Atomic Oxygen on Ag(100): A Density Functional Theory Study

CO oxidation by molecular and atomic oxygen has been studied using Ag38 and Ag29 cluster models at the DFT-PW91PW91/[LANL2DZ, 6-31G(d)] level. The calculated results show that the adsorptions of O atom, O2, and CO molecule on the silver (100) surface are all of chemical type but relatively weak for CO and O2 molecule with the adsorption energy of 8.7 and 2.7 kcal/mol, respectively. Upon the adsorption on silver, O2 molecule was partially activated and ready to participate in the CO oxidation reaction through an L–H mechanism. The reaction involves breaking of the O–O bond and forming a C–O bond. The interactions between the 2s and 2p of C and O, and 4d of Ag orbitals facilitate the CO oxidation on silver. However, the CO oxidation by atomic oxygen slightly favors an E–R mechanism since the adsorption of CO is very weak and its calculated molecular properties identify itself more like free CO. For CO3, it is a fairly stable intermediate, but it can be removed by CO or through dissociation, showing this rea...