Local reactivity of thin Pd overlayers on Au single crystals

The local reactivity of thin pseudomorphic Pd overlayers on Au(111) and (100) single crystal surfaces has been studied by periodic density functional theory calculations within the generalized gradient approximation. We have determined the adsorption energies of atomic hydrogen and of CO as a microscopic probe of the reactivity. We demonstrate that both surface strain effects and substrate interaction effects contribute to the modification of the reactivity of the overlayer system. While there is no unique trend in the adsorption energies as a function of the lattice strain, at all considered adsorption sites we find a maximum of the binding energies of both H and CO on two Pd overlayers on Au thus providing a microscopic explanation for recent experiments on the electrochemical reactivity of flat Pd nanoparticles on Au(111). Furthermore, we address the initial stages of Pd deposition on Au.