Density Functional Study of Sequential H2 Dissociative Chemisorption on a Pt6 Cluster

The dissociative chemisorption of dihydrogen on a Pt6 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 H2 molecules via the overlap of 5d orbitals of Pt6 and 1σ* orbital of H2 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.