Dissolution of partially immersed nickel during in situ oxidation in molten carbonate: Cyclic, stripping and square wave voltammetry measurements

Electrochemical techniques such as cyclic voltammetry, stripping voltammetry and square wave voltammetry were used to determine the product of concentration and diffusivity of Ni²⁺ ions in 62% Li₂CO³ + 38% K²CO₃ electrolyte mixture under standard gas composition(15% O₂ + 30% CO₂) at 650°C. In the case of cyclic voltammetry and stripping voltammetry, dissolved nickel is first deposited on a gold electrode at negative potentials, then dissolved by scanning through positive potentials. Square wave voltammetry is also used as a more precise method to compare the cD^1/2 product between electrochemical techniques. The magnitude of the peak current from current-potential data is related to scan rate, diffusivity and concentration of nickel ions in the melt. Values of cD^1/2 obtained by these techniques are in good agreement. The saturation concentrations calculated from our measurements (0.5-1 μmol cm³) depend on the diffusion coefficient used in the calculations, but agree with literature values in order of magnitude.