Investigation of Carbon Monoxide Adsorption on Cationic Gold-Palladium Clusters

Density functional calculations have been performed for the carbon monoxide molecule adsorption on Au_nPd_m⁺ (n + m ≤ 6) clusters. In the process of CO adsorption, small Au clusters and Pd clusters tend to be an Au atom and three Pd atoms adsorption, respectively. For the mixed Au–Pd clusters, an Au atom, a Pd atom, two atoms consisted of an Au atom and a Pd atom, two Pd atoms, and three Pd atoms adsorption structures are displayed. The highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) gaps and natural bond orbital charge population are calculated. Moreover, CO adsorption energy, CO stretching frequency, and CO bond length (upon adsorption) are also analysed in detail. The results predict that the adsorption strength of Au clusters with CO and the C–O vibration strength is enhanced and reduced after doping of Pd in the Au_nPd_mCO⁺ complexes, respectively.