Abstract:

Adsorption of CO onto Pdn (n=1-8) clusters was systematically investigated using density functional theory. Results indicate that the lowest energy structures of PdnCO are still generated when CO is adsorbed onto Pdn clusters. We found that among the molecular adsorption states, a weakly bound state with end-on type geometry is the most energetically favorable. The lowest energy structures of Pdn clusters are not changed by adsorbing CO molecules. Chemisorption of CO onto Pdn cluster surfaces is a non-dissociative adsorption process. An increased theoretical CO bond length of 0.1167-0.1168 nm in PdnCO cluster (compared to 0.1166 nm in free CO molecule) indicates a small activation for the CO bond except for the case where n=2. Natural bond orbital analysis shows that the interaction between a Pd atom and a CO molecule is small. The second-order energy difference shows that Pd4CO and Pd6CO clusters have enhanced stabilities.

Key words: PdnCO and Pdn clusters, Density functional theory, Geometry, Electronic property