Electrochemistry of cobalt ethylenediamine complexes at high pH

Abstract

The electrochemical behavior of cobalt ethylenediamine complexes (Co(en)), at pH 12 was investigated by cyclic voltammetry (CV), the potentiostatic pulse technique and polarization curve measurements at stationary and rotating glassy carbon (GC) electrodes. It was shown that sixteen different species could be formed in a solution containing Co(en)3, with the most stable one at all pH values being [Co(en)3]3+. The reduction of [Co(en)3]3+ into [Co(en)3]2+ was shown to be a totally irreversible, one-electron exchange reaction. Further reduction of [Co(en)3]2+ was found to be a complex process leading to cobalt deposition at potentials more negative than -1.45 V vs. SCE. The process of [Co(en)3]2+ oxidation was also complex and most probably coupled with chemical reactions.