Variation of the potential of zero charge for a silver monolayer deposited onto various noble metal single crystal surfaces

The potential of zero charge (PZC) of a pseudomorphic silver monolayer electrodeposited onto Au(1 1 1), Pt(1 1 1), Pd(1 1 1), Ir(1 1 1) and Rh(1 1 1) has been determined in diluted perchlorate solution by measuring capacitance–potential curves. The PZC of these Ag overlayers varies in the potential range between −0.8 V and −0.45 V versus SCE depending on the nature of the substrate material and thus reveals significant shifts compared to −0.7 V versus SCE for a massive Ag(1 1 1) electrode. This bulk value for the PZC has also been obtained for two monolayer thick Ag overlayers, demonstrating that mainly the first monolayers are electronically altered by an underlying foreign substrate. In addition, the PZC of thicker deposits has always been found to be identical to the PZC of Ag(1 1 1), showing an epitaxial growth of Ag on the electrodes under study. While no dependence on the lattice constants of the substrates for the PZC of the pseudomorphic Ag monolayers was found, it has been observed that calculated shifts in the d-band centre show the same systematic variation. Work function data for Ag monolayers on Au(1 1 1) and Pt(1 1 1) are in good agreement with the measured PZC values. Consequences of altered double-layer properties on electrocatalytic reactions are briefly addressed.