Silver nucleation on mercaptoacetic acid covered gold electrodes

Silver nucleation on the mercaptoacetic acid coated gold electrode under potentiodynamic and potentiostatic conditions was investigated using cyclic voltammetry, chronoamperometry, scanning electron microscopy, and mathematical simulations. Silver was easily adsorbed on the modified electrode surface due to the complexation and electrostatic interaction of silver with the carboxyl groups of mercaptoacetic acid. The rate constants for the electrochemical reduction and oxidation of silver on the mercaptoacetic acid coated gold electrode were evaluated. The variation of the site density of silver nucleus with the deposition potential, the dependences of the nucleation rate on the deposition potential and on the driving force (the concentration of silver) were investigated. The deposition potential affected the activity of the nucleation sites but the driving force did not. These variations were explained by the existence of a distribution of site energies (mercaptoacetic acid molecules) on the electrode surface. (c) 2007 Elsevier Ltd. All rights reserved.