Adsorption of Ethylene, Vinyl, Acetic Acid, and Acetate Species on PdAu(111) and PdAu(100) Surface Alloys: A Cluster Model Study

The adsorption properties on PdAu surface alloys of ethylene and acetic acid molecules along with their derived vinyl and acetate surface species have been investigated by density functional theory calculations. Large clusters have been used to model second-neighbor Pd monomer pair ensembles on PdAu(100) and PdAu(111) surface alloys. Ethylene and acetic acid are weakly bonded to the Pd monomers, while vinyl and acetate are strongly bonded to both Pd and Au atoms being very stable surface species. The ligand effect of the gold atoms surrounding the Pd monomers has been shown to be stronger in the more dense PdAu(1 11) surface alloy. Cluster model results are in good agreement with experimental evidence providing important insight on the adsorption bonding modes, the assignment of the infrared features, and the preferred adsorption sites.