Ruthenium Cluster Structure Change Induced by Hydrogen Adsorption: Ru₁₉^–

The effect of hydrogenation on the structure of Ru 19 – has been studied using a combination of trapped ion electron diffraction and density functional computations. While the bare Ru 19 – cluster has a closed-shell octahedral geometry, hydrogenation of the cluster changes the structure type of the ruthenium core toward an icosahedral motif. The experiments show a gradual structural transition depending on the number of adsorbed hydrogen atoms. Density functional theory computations reveal the driving force behind this process to be the larger hydrogen adsorption energies for the bi-icosahedral structure and predict a corresponding structural rearrangement at around 20 adsorbed hydrogen atoms, which is consistent with the experimental findings. Additionally, the computations provide insight into the hydrogen-binding situation. They show that hydrogen is preferentially atomically bound only to surface Ru atoms. H 2 binding is predicted only at high hydrogen loadings.