The adsorption of oxygen on bimetallic Pd3M2 clusters (M = Ag, Au, Co, Cu, Mn, Ni, Pt, and Ru) with and without alumina support by density functional theory

We performed density functional theory (DFT) calculations to systematically investigate the adsorption of atomic and molecular oxygen on the bimetallic Pd3M2 clusters (M = Ag, Au, Co, Cu, Mn, Ni, Pt, and Ru) supported on hydroxylated alumina. The interaction between the atomic and molecular oxygen with unsupported Pd3M2 clusters was also computed for comparison. It was found that oxygen molecule dissociates spontaneously upon adsorption on Pd3Co2, Pd3Mn2, and Pd3Ru2 for both unsupported and hydroxylated alumina-supported situations. For all other cases, the bond length of molecular oxygen is activated to a superoxo state upon adsorption. Bader charge analysis revealed that when the charge transfer to the antibonding pi orbital of the oxygen molecule was greater than -1.3 electrons, the oxygen molecule dissociated spontaneously. The study of the adsorption of atomic oxygen on the hydroxylated alumina-supported clusters showed that the adsorbed oxygen atom spontaneously picks up H-atom from the substrate for all cases forming OH and representing a reverse H-spillover except for the Pd3Ru2 cluster. Water molecule is formed when atomic oxygen is adsorbed on hydroxylated alumina-supported Pd3Mn2 cluster due to the spontaneous pick up of two H-atoms from the substrate by the adsorbed atomic oxygen.