THE INFLUENCE OF FOREIGN CATIONS ON THE ELECTROCHEMICAL-BEHAVIOR OF THE NICKEL-HYDROXIDE ELECTRODE

The influence of Co, Cd, and Zn ions on the voltammetric behavior of the nickel hydroxide electrode in binary and ternary metal hydroxide layers in 0.1M KOH and 0.08M KOH + 0.02M LiOH was investigated. The presence of Co hydroxide increases the reversibility of the Ni(II)/Ni(III) electrochemical reaction and hinders aging effects involving unstable Ni hydroxide species. The simultaneous presence of Co and Zn ions in the metal hydroxide layer has a beneficial influence for the long-term stability and efficiency of the active material. The incorporation of Cd hydroxide increases the polarization of the oxygen evolution reaction. Results are interpreted in terms of either the existence of intermediate oxidation level of the foreign cations which can be produced at potentials lower than the equilibrium potential of the Ni hydroxide electrode or the influence of the foreign metal hydroxide on the oxygen evolution reaction.