Theoretical Calculations on the Oxidation of CO on Au55, Ag13Au42, Au13Ag42, and Ag55 Clusters of Nanometer Size

Using density-functional theory (DFT), we investigated the oxidation of CO on Au-55, Ag13Au42, Au13Ag42, and Ag-55 metal clusters of nm size. The structures of oxidation intermediates and at the transition states on the potential-energy surfaces were derived with the nudged-elastic-band (NEB) method. According to our results, the coupling of CO and O-2 molecules to form intermediate OCOO has the least energy barrier (0.13 eV) on the Ag13Au42 core-shell nanocluster, whereas the dissociation of the O - O bond of OCOO to form CO2 and O on the Au13Ag42 core-shell nanocluster is the easiest process with a 0.15 eV barrier height. To understand the electronic property of these nanocluster catalysts and their interactions with the adsorbates, we calculated the electron localization functions, Bader charges, and local densities of states; the results were consistent and explicable.