Density functional study of sequential H2 dissociative chemisorption on a Pt6 cluster

The dissociative chemisorption of dihydrogen on a Pt-6 cluster with an octahedral configuration was studied with density functional theory. The on-top site was identified to be the most favorable chemisorption site for dihydrogen followed by the bridge site and the 3-fold hollow site. It was found that the dissociative chemisorption process is dictated by the charge transfer from the Pt cluster to H-2 molecules via the overlap of 5d orbitals of Pt-6 and 1 sigma* orbital of H-2 and that the cluster achieves its full saturation with H atoms at the Pt/H ratio of 1:4. The effect of H coverage on the Pt cluster catalytic activities was discussed.