On the Sequential Hydrogen Dissociative Chemisorption on Small Platinum Clusters: A Density Functional Theory Study

We present a simple cluster model to understand the dissociative chemisorption of molecular hydrogen and the desorption of atomic hydrogen on platinum small clusters using the gradient-corrected density functional theory. Successive H 2 decomposition and sequential H desorption on the selected Pt n ( n = 2−5, 7−9) clusters were systematically studied, and the H 2 dissociative chemisorption energies and the H desorption energies at the full H saturation were identified. The reaction processes are driven by charge transfer from Pt atoms to H atoms assisted by strong orbital overlaps between Pt 5d orbitals and H 1s orbital, which leads to electron delocalization in large clusters of metal hydrides. It was found that the number of H atoms chemisorbed on the small Pt clusters increases almost linearly with the size of the selected Pt cluster.