Electrochemistry of cobalt ethylenediamine complexes at high pH

Abstract

In this work the electrochemical behavior of cobalt ethylendiamine complexes (Co(en)), at pH 12 has been investigated by cyclic voltammetry (CV), potentiostatic pulse technique and polarization curve measurements at stationary and rotating glassy carbon (GC) electrode. It was shown that sixteen different species can be formed in the solution containing Co(en)3 ligand, 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 totally irreversible, one-electron exchange reaction. Further reduction of [Co(en)3]2+ was found to be complex process leading to a cobalt deposition at the 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 the chemical reaction. [Projekat Ministarstva nauke Republike Srbije, br. 172045]

Keywords

• Distribution of Co(en)3 complexes
• irreversible reduction of [Co(en)3]3+/[Co(en)3]2+
• reduction of [Co(en)3]2+ to Co