Hydrogen sequential dissociative chemisorption on Ni _n(n = 2∼9,13) clusters: Comparison with Pt and Pd

Hydrogen dissociative chemisorption and desorption on small lowest energy Ni _n clusters up to n;=;13 as a function of H coverage was studied using density functional theory. H adsorption on the clusters was found to be preferentially at edge sites followed by 3-fold hollow sites and on-top sites. The minimum energy path calculations suggest that H ₂ dissociative chemisorption is both thermodynamically and kinetically favorable and the H atoms on the clusters are mobile. Calculations on the sequential H ₂ dissociative chemisorption on the clusters indicate that the edge sites are populated first and subsequently several on-top sites and hollow sites are also occupied upon full cluster saturation. In all cases, the average hydrogen capacity on Ni _n clusters is similar to that of Pd _n clusters but considerably smaller than that of Pt _n clusters. Comparison of hydrogen dissociative chemisorption energies and H desorption energies at full H-coverage among the Ni family clusters was made.