Tuning adsorption via strain and vertical ligand effects.

We report on the structure and electrochemical adsorption properties of well-defined pseudomorphic Pt mono- and multilayers on Ru(0001). These act as model surfaces for Pt(111) with slightly decreased affinity to adsorbed hydrogen (H(ad)) and hydroxyl (OH(ad)). In cyclic voltammograms, this is reflected in more negative/positive potential regions for the reversible adsorption of upd-H(ad)/OH(ad), respectively, compared to Pt(111). For upd-H(ad), we show that the corresponding trends can be predicted with high accuracy by density functional theory (DFT). In particular, the upd-H(ad) onset regions can be precisely simulated using the H(ad) adsorption energies from DFT, the layer thickness distribution from STM, and the base voltammogram of Pt(111) as reference.