Selectivity of Pd-Functionalized PtNi(111) Surface: cis -3-Hexenoic Acid Adsorption

Abstract

Vienna Ab-initio Simulation Package (VASP) is employed to study the adsorption of the monounsaturated cis-3-hexenoic acid (cis-C5H9COOH) on a bimetallic surface compound of a Pd-functionalized layer of Pt on Ni(111). The cis-3-hexenoic acid is much distorted on Pt than Pd surface atoms. The molecule interacts through the C = C bond but also presents an important contact via the COOH group; consequently, the carboxyl group results partial dissociate. In addition, Pd favors H removal. The surface-molecule interaction is most stable on Pd-functionalized PtNi(111) (−6.36 eV) than unfunctionalized PtNi(111) (−2.40 eV). Calculations show that Pd atoms stabilize the π modes better than Pt. The overall adsorption energy is a compromise between the distortion energy of the molecule on Pt atoms and the stabilization due to the interaction between the molecule and Pd surface atoms.