Behaviour of nitrate impurity in nickelcadmium cells

Abstract

The oxidation-reduction behaviour of NO3−, NO2−, N2O22−, NH2OH and NH3 at a platinum electrode in alkaline solution has been investigated using cyclic voltammetry. The results have been compared with the corresponding behaviour of these species at charged, porous cadmium and nickel hydroxide electrodes in order to understand the likely behaviour of NO3− impurities in nickelcadmium cells. The reactions are shown to be irreversible processes and strongly dependent on the nature of the electrode surfaces. The reactions which are likely to be involved in a charged cell can be represented by the overall scheme: $${\text{NO}}_{\text{3}} ^\_ {\text{NO}}_{\text{2}} ^\_ {\text{NH}}_{\text{3}} \xrightarrow{{{\text{slow}}}}{\text{N}}_2 $$ It is suggested that the self-discharge of cells containing NO3− is limited by slow kinetic effects rather than by diffusion as previously supposed.