Optical and Electrochemical Studies of Underpotential Deposition of Lead on Gold Evaporated and Single-Crystal Electrodes

Abstract

Linear sweep voltammetry and reflectance spectroscopy have been used to examine the underpotential deposition of lead on gold in Pb2+ containing HClO4 solutions. The voltammetry curves and reflectance-change data provide evidence that the lead is first deposited as ions although their effective ionic charge is probably reduced substantially from +2 through their strong interaction with the band structure of the gold substrate. At more cathodic potentials, still well below the reversible potential of bulk lead, a sharp transition is observed over a 5-10 mV range. On the basis of the reflectance and voltammetry data, this transition appears to involve a two-dimensional phase transition leading to a metalliclike lead layer. Adsorption isotherms have been evaluated from the reflectance changes. Alternating potential electro-modulation techniques and complex plane analysis have been used to examine the kinetics of the lead adsorption-desorption and to evaluate the apparent exchange current density for the process. © 1974, The Electrochemical Society, Inc. All rights reserved.