The nickel electrode in liquid ammonia

Abstract

The formal standard potential of nickel in 1 M ammonium nitrate solution in liquid ammonia is E o' (Ni 2+/Ni) = 6 (±12) mV vs. a standard hydrogen electrode. The absorption spectra of nickel(II) in liquid ammonia are very similar to those of the complex Ni(NH 3) 2+ 6 in aqueous solution. The charge-transfer rates of dissolution and deposition of nickel in solutions of ammonium chloride, ammonium nitrate or lithium perchlorate were independent of the electrolyte composition. The anodic and cathodic transfer coefficients α + = 0.65 and α − = 0.36, respectively, assuming a charge number z = 2, were independent of the temperature. The standard exchange current density in 1 M ammonium nitrate base electrolyte at 273 K was 63 μA/cm 2. The mechanism is characterized by the transfer of Ni 2+ in one step. The corrosion rates of active nickel in several electrolyte solutions were determined. Unlike iron, nickel does not passivate in liquid ammonia, but salt layers prevent unlimited growth of the anodic current density.