Density Functional Study of the Interactions between Dihydrogen and Pdn (n = 1−4) Clusters

Abstract

The dihydrogen interactions with Pdn (n = 1−4) clusters was investigated using hybrid density functional Becke3LYP method and two ECP basis sets. The local minima configurations for a number of H2 molecule approach modes toward Pdn clusters are presented. Some of these states may be interpreted as a physical adsorption and others as dissociative interaction of the H2 molecule with the palladium cluster. Both geometric and energetic characteristics of weakly bonded pre-dissociated complexes on Pd3-4 clusters are very close to those on a bulk Pd (111) surface, while the stable states with dissociated hydrogen molecules show significant differences. In contrast to the bulk surface, 2-fold coordination positions exhibit slightly higher stability of hydrogen bonding in Pd3 and Pd4 clusters than 3-fold ones. The binding energy is significantly higher for small clusters than for the bulk surface. The Pd2 cluster was found to be the most active toward hydrogen capture in accordance with the experimental results.