Comparing the binding energies to oxygen it is evident that the latter is more stable than the former; as explained in the next section, O 2 dissociation is an exothermic process. Overall CO is more strongly adsorbed than molecular oxygen. The same is true for atomic oxygen in monometallic and Pt4Ge clusters. However, as the Ge concentration increases, the adsorption of 2 ) state with a O-O bond distance of ~1.47 Å (bond order ~1.0). Our calculations suggest a large oxygen activation for the PtGe nanoclusters. The internal bond is increased up to 1.47-1.50 Å in the bidentate bridge configuration, indicating the presence of a peroxo state; while in the top configuration it is only activated until the superoxo state with a bond length of 1.37 Å. We believe that such a high activation translates into low oxygen dissociation barriers.