Using density-functional theory (DFT), we investigated the oxidation of CO on Au 55, Ag 13Au 42, Au 13Ag 42, 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 Ag 13Au 42 core-shell nanocluster, whereas the dissociation of the O-O bond of OCOO to form CO 2 and O on the Au 13Ag 42 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.
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