Oxidation of small gas phase Pd clusters: A density functional study

The adsorption sites of O2 on neutral PdN clusters (N = 1-4) were studied using spin density functional theory. Only for Pd1O2 molecular adsorption is found to be favorable. For Pd2-4O2 dissociative adsorption with the oxygen sitting on Pd bridge sites is preferred. Most Pd clusters remain in the same high spin states found for pure gas phase Pd clusters. Only the ground state of Pd4O2 increase its spin from a triplet to a quintet state. For molecular adsorption the O-O bond gets activated to a superoxo-like state.