Copper underpotential deposition on ethanethiol-modified Au(111) electrodes: kinetic effects

The kinetics of copper underpotential deposition from sulfuric acid solutio ns onto ethanethiol-modified Au(III) electrodes was studied by cyclic volta mmetry. We show that Cu underpotential deposition does indeed take place, a lthough the current peak representing underpotential deposition, i.e. the d eposition of the first Cu monolayer, is shifted into the overpotential rang e for commonly employed sweep rates. However, holding the potential in the underpotential range close to the Nernst potential for more than 1 h result s in the formation of a complete Cu monolayer. We therefore conclude that, kinetically severely hindered, the Cu monolayer is formed at the Au(111)/SA M interface. Because voltammetric experiments with SAM-covered electrodes a re always prone to some degree of irreproducibility, we address the influen ce of monolayer defects on cyclic voltammograms in a more systematic way. ( C) 1999 Elsevier Science Ltd. All rights reserved.