Kinetics of Electrode Reactions in Liquid Ammonia: Part 4.—The Cun/Cu'/Cu° System in Acid Solution

Abstract

The Cu^/Cu1 redox system is fully reversible on gold or platinum electrodes and quasi-reversible on vitreous carbon. When the metal electrodes are anodically oxidised prior to the measurements, the redox process is inhibited and curvature in the polarisation data indicate that the electrodes behave as p-type semi-conductors. The system Cui/Cu° possesses unusual features. Whereas the dissolu tion of Cu° to Cu1 is quasi reversible (Xr0 = 8xl0-5cms-1) the deposition reaction is severely inhibited by the formation of unidentified insulating films which also retard the reduction of Cu11 to Cu1. This result explains the poor quality of electrodeposits of copper from ammonia solutions described in the older literature.