Strain and Low-Coordination Effects on Monolayer Nanoislands of Pd and Pt on Au(111): A Comparative Analysis Based on Density Functional Results

Recent experiments demonstrated that the catalytic centers for the hydrogen evolution reaction (HER) are different on Pd and Pt nanoislands on Au(111). Inspired by these experiments, we examined the geometric, energetic, electronic, and hydrogen adsorption properties of monolayer model nanoislands of Pd and Pt supported on Au(111) with density functional theory calculations. Accordingly, Au tensile strain effects can be nearly 50% larger on the geometric structure of nanoislands of Pd on Au(111) than on their Pt analogues, resulting in different electronic properties for these nanoislands. Despite these differences between Pd and Pt nanoislands on Au(111), our computational modeling of the hydrogen adsorption suggests that the unique catalytic centers for the HER on Pd and Pt nanoislands supported on Au(111) are derived from the existence of low-coordinated adsorption sites and the intrinsic properties of Pd and Pt, but not from Au tensile strain effects.