Plasma Electrochemistry in Radio Frequency Discharges : Oxidation of Silver in a Chlorine Plasma

Abstract

Plasma-anodic experiments on the oxidation of silver electrodes were performed in an inductively coupled chlorine plasma in the temperature range between 50 and 180°C. Pure chlorine plasmas with gas pressures on the order of 1 mbar were employed. The growth rate of the silver chloride films was strongly enhanced in the plasma compared to thermal conditions, and it could be controlled effectively by applying an external electric potential under both galvanostatic and potentiostatic conditions. An analysis of the growth kinetics of the silver halide film shows that the growth rate is limited by the electron flux across the product film in the thermal experiment and across the plasma in the plasma-anodic experiment. It is experimentally shown that the thickness of the product layer is proportional to the electrical charge passed through the plasma-electrochemical cell Ag/AgCl/plasma/carbon. Current densities across the product layer were in the order of The enhancement of the growth rate is smaller than predicted by Faraday’s law, indicating either electronic leakage currents or anode sputtering. © 2003 The Electrochemical Society. All rights reserved.