Theoretical calculations on the oxidation of CO on Au ₅₅, Ag ₁₃Au ₄₂, Au ₁₃Ag ₄₂, and Ag ₅₅ clusters of nanometer size

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.