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 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 electromodulation 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.