Electrochemical behavior and detection of Ni2O3 dissolved in molten enamel at a platinum electrode by means of cyclic, square wave and hydrodynamic voltammetry

It is shown that the reversible wave with E1/2 = −0.54 V vs. ZrO2/Pt/air observed at a platinum disc electrode in molten enamel can be attributed to the Ni(II)/Ni(0) system with n = 2. Ni(0) is not deposited on the surface of the platinum electrode but is soluble in the molten enamel. Proof for reversibility and the fact that n = 2 is given in detail. Detection of Ni(II) concentrations in enamel melts can be performed by using transport-controlled peak currents in cyclic and square wave voltammetry or by using limiting currents in chronoamperometry at a rotating disc electrode. These methods are optimized as regards sensitivity and detection limit for Ni(II) determination. Transient methods in combination with a rotating disc electrode cannot be applied because of slow diffusion of the reacting species resulting in long times before a steady state is obtained.