Theoretical Study of Interaction between Hydrogen and Small Pt-Sn Intermetallic Clusters

Small clusters, which simulate the active sites of Pt-Sn intermetallics exhibiting a high level of activity and selectivity in the deoxygenation reaction of esters without the loss of carbon mass to form C-1, C-2, and carbon oxides, are constructed and studied with the density functional theory. Molecular adsorption of hydrogen, dissociation of hydrogen molecules at Pt sites, and transition of adsorbed hydrogen atoms from Pt to Sn are considered. The introduction of Sn significantly decreases the affinity of platinum to hydrogen, so that the transition of H atoms to Sn atoms is facilitated with the increase in the amount of Sn. A comparison of the activation energies for such a transition with those of the possible association of hydrogen atoms on tin and the molecular desorption of H-2 showed that the hydrogen spillover in the Pt-Sn intermetallics should not lead to a significant accumulation of hydrogen on tin. In other words, in contrast to Pt atoms, Sn atoms probably cannot serve as active sites of hydrogen adsorption in the deoxygenation reaction.