CYCLIC VOLTAMMETRIC STUDIES OF PURE AND DOPED FILMS OF COBALT HYDROXIDE IN 1-M KOH

Cyclic voltammetric studies of electrosynthetically prepared pure and doped thin films of cobalt hydroxide (on a platinum foil substrate) in 1 M KOH show that Co(OH)2 undergoes a quasi-reversible redox reaction between a nearly quadrivalent black oxidic phase and a trivalent brown bronze-like phase. The coulombic efficiency is 60%. A common scheme is proposed for the electrode reactions of oxide electrodes in alkaline media, namely: M(II)(OH)2 reversible HM(III)O2 reversible M(IV)O2, where M = Mn, Co, Ni. The three metals execute different steps in this two-electron redox reaction, either reversibly or quasi-reversibly. Based on this scheme, new compounds are suggested as possible electrode materials for secondary storage battery systems. The effect of eight, different, dopant metal ions on the redox reactions of Co(OH)2 is investigated. Only La3+ ions are found to influence favourably the performance of Co(OH)2 as an electrode material.