Computational study of the adsorption of bi-metallic clusters

It was shown that small silver clusters can control the rate of LiO₂ formation in Li-O₂ batteries. The gap near the fermi energy was shown to control the oxygen reduction, an important reaction for LiO₂ formation. Controlling the gap would ultimately control the rate of LiO₂ formation. One can vary the size of the cluster to control the gap, however, this “knob” provides limited variance. Alloying, in combination with size variation offer a much wider control of the LiO₂ formation. Here, we investigate the effect of Pd₃M₂ (where M varies from Ag, Au, Co, Cu, Mn, Ni, Pt, and Ru) clusters on the rate of O₂ reduction at the hydroxylated alumina surface. Using DFT, we calculated the binding energies of these clusters on the alumina substrate which ranges from depending upon the composition of the alloy-cluster, its orientation and the adsorption site. We also find that Pd atom binds strongly with the substrate oxygen atom with a short bond-length of about 2.2 . We explore how the gap between the HOMO of the cluster and the Fermi energy of the system varies as a function of elemental composition. These preliminary results will open the door for more systematic studies of alloy clusters of different size and stoichiometry.