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

摘要

Linear sweep voltammetry and reflectance spectroscopy have been used to examine the under potential deposition of lead on gold in Pb(2+) containing HC104solutions. 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 +2through 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 5to 10mV range. This transition appears to involve a two dimensional phase transition leading to a metallic-like lead layer. Adsorption isotherms have been evaluated from the reflectance changes. A.c. 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. (Modified author abstract)