Oxidation of electrodeposited cobalt electrodes in an alkaline electrolyte

Abstract

The oxidation of electrodeposited Co electrodes has been studied in 0.1 M KOHaq at potentials more negative than -880 mV vs. Hg|HgO by means of electrochemical quartz crystal microbalance (EQCM) and rotating ring disk electrode coupled with cyclic voltammetry (CV) and chronoamperometry (CA). Dissolution of cobalt was found to be insignificant and does not constitute a step in the overall process of formation of the oxidised layer. The irreversibility of the oxidation process depends on the electrode potential and oxidation time. The composition of the oxidised layer depends on the oxidation potential: Co(OH)2 is formed at more negative potentials, while at more positive potentials CoO is the prevailing product. The results obtained by means of three techniques (CV, CA and EQCM) reveal that at potentials not higher than -880 mV, the oxidation of Co follows a direct logarithmic law. The mechanism of the process is discussed. © 2012 The Author(s).