The electrochemical behaviour of the nickel oxide electrode.

Abstract

The nickel oxide electrode and its electrochemical properties have, for the most part, been ill characterized largely due to a lack of appreciation of the variable stoichiometry of the oxidized material and of the nature of the electrode processes occurring at the nickel oxide interface. In the present work a systematic attempt has been made to elucidate, using modern approaches in electrode kinetics: (a) the mechanism of oxygen evolution both on an odic polarization and open-circuit self-discharge; (b) the quantitative nature of the self-discharge process as an example of a mixed electrode reaction system analogous to corrosion; (c) the true thermodynamic reversible potentials of the nickel oxide electrode in a formal state of oxidation NiO 1.25 as a function of activities of KOH and water in the electrolyte. The measurement of true rates of self-discharge on open-circuit has necessitated the development of a new technique for the microvolumetric determination of oxygen evolution rates. Measurements have also been made of e.m.f. decay on open-circuit and these measurements in conjunction with true self-discharge rates obtained by microvolumetric techniques have permitted a critical examination of the significance of e.m.f. decay rates. It has been Shown that the simple theory previously proposed is inadequate to explain the open.-circuit e.m.f. behavior of the nickel oxide electrode. A general discussion of e.m.f. decay kinetics is given. Al