Solution Redox Couples for Electrochemical Energy Storage: II . Cobalt(III)‐Cobalt(II) Complexes with o‐Phenanthroline and Related Ligands

Co(III) and Co(II) complexes with o‐phenanthroline, bipyridine, and related ligands were examined by voltammetric and coulometric techniques in aqueous media to investigate their suitability as redox couples for electrochemical energy storage systems and semiconductor photoelectrochemical cells. The Co(II) complex undergoes a rapid one‐electron oxidation at a graphite or platinum electrode to yield the Co(III) complex. With several ligands both forms of the couple are very stable and show formal potentials shifted very negative (to ∼0.1V vs. SCE) from that of the aquo‐Co(III/II) couple.