CO₂ Hydrogenation on Gas-Phase Palladium-Zinc Bimetallic Clusters

Hydrogenation of CO₂ to valuable products is an attractive method to mitigate the greenhouse effect. Palladium-zinc-based nanomaterials are stable and selective catalysts in the methanol formation process. For a better understanding of the catalytic reaction mechanisms, here, we investigate hydrogen activation and carbon dioxide hydrogenation on Pd _x Zn _x (x = 2-4) and Pd₆ clusters using systematic density functional theory analysis, selected on the basis of high-level benchmarks. We show that alloying palladium with zinc makes the H₂ adsorption and dissociation less favored and increases the energies of the highest lying transition states, while zinc strongly stabilizes the formate intermediate, by binding one of its oxygen atoms through a (partial) ionic bond.