Collect. Czech. Chem. Commun. 1997, 62, 696-708

Er-pH and Er-mKOH Diagrams for Nickel at 25 °C

Jan Baleja and Jiri Divisekb

a Consultant Bureau for Chemical Engineering, Johanniterstr. 28, 86609 Donauworth, Germany
b Research Centre Julich (KFA), 52425 Julich, Germany


Based on the conclusion that no Ni(III) oxo compounds can exist in oxidized nickel oxide electrodes with the total oxidation number 2.0 < zNi < approx. 3.6 and that non-ideal solid solutions with a formal composition (1 - X2) Ni(OH)2.X2NiO2. xH2O are involved, Er-pH and Er-mKOH diagrams at 25 °C were calculated and graphically represented using the thermodynamic standard data determined for hypothetical NiO2.x H2O. The calculations were performed assuming aH2O = 1 in the entire pH range (Er-pH diagram) and considering the true water activity in KOH solutions of various concentrations (Er-mKOH diagram).

Keywords: Nickel oxide electrodes; Er-pH diagram; Er-mKOH diagram.