A first-principles periodic super-cell analysis was made of oxygen adsorption, diffusion and dissociation at the kinked Pt(321) surface. Binding energies and binding site preferences of isolated oxygen atoms and molecules were determined, and it was shown that both atomic and molecular oxygen prefer binding in bridge sites involving coordinatively unsaturated kink Pt atoms. The binding energies of atomic and molecular oxygen in different sites correlated well with the average metallic Pt coordination number of Pt atoms forming each site, although differences exist between adsorbates in symmetrically similar sites due to the inherent chirality of the surface. Atomic O in the strongest binding bridge sites experiences relatively small energy barriers for diffusion to neighboring sites compared to O on Pt(111). However, due to the structure of the surface, O diffusion was only rapid between different sites around the kink Pt atom, whereas the effective long-range tracer diffusion, as determined from a simple course-grain model, was shown to be anisotropic and slower than on the Pt(111) surface. Four dissociation pathways for O(2) at low coverage were also reported and found to be in agreement with experimental observations of facile dissociation, even at low temperature.

Potential Energy Surfaces for Oxygen Adsorption, Dissociation, and Diffusion at the Pt(321) Surface. J.M.Bray, W.F.Schneider: Langmuir, 2011, 27(13), 8177-86