Kinetics of Electrode Reactions in Liquid Ammonia: Part 2.—FeIII/FeII and CoIII/CoII redox couples

Abstract

Polarisation data has been obtained for the CoII/CoIII and FeII/FeIII couples at rotating disc electrodes of platinum, gold and vitreous carbon at – 30°C in ammonia acid solution. In addition, metal wires and carbon rod have been used to examine the low level behaviour of the cobalt system and to record charge measurements in the oxidation of the anode surfaces. The iron couple is reversible on carbon but is inhibited by anodic films on gold and platinum. Apparent standard rate constants for the CoII/CoIII reaction are affected only slightly by the electrode material, but the oxidation branch is noticeably inhibited by anodic film formation. The mechanism of inhibition by anodic films is discussed. FeIII is unstable in acid ammonia.