The interaction of atomic oxygen with small copper clusters. A theoretical approach.

A theoretical study of atomic oxygen adsorption on small Cu-n (n <= 8) clusters was carried out using density functional methods. The copper-oxygen system is important to understand the mechanism of the oxygen oxidation catalyzed by copper. It is found that the oxygen reactivity is strongly dependent of the size of copper clusters and Cu-n with n odd exhibiting the highest reactivity. The adsorption energy has values from 37 to 93 kcal/mol. In general, in clusters With even number of atoms the oxygen adsorption is carried out on a top type site, on the other hand, in clusters with odd number of atoms the adsorption is carried out on highly coordinated sites. In comparison with bare Cu-n. clusters, the relative stability of copper clusters under oxygen adsorption is not largely affected, exhibiting only small modifications in the structure of the cluster. Electronic and symmetrical effects seen to govern the oxygen adsorption process.