Impedance investigation of the mechanism of copper electrodeposition from acidic perchlorate electrolyte

Abstract

The mechanism of the copper electrodeposition from acidic perchlorate electrolyte has been investigated with polarization and impedance methods. The impedance of the copper electrode in copper perchlorate electrolytes has been measured as a function of frequency for different E dc overpotential values and different copper(II) ion concentrations. The relations between the shape of a complex plane impedance display and the copper electrode potential values as well as the concentration of Cu II ion were analysed in terms of the electrode reaction mechanism. It is shown, that the presence of the intermediate cuprous ion and its sinusoidal change of transport rate is one of the main factors determining the depressed shape of the impedance arc. The quantitative relation between the faradaic impedance and the rates of electrode reaction rates was established. The impedance arc was simulated with a set of parameters involving: rate constants, Tafel slopes, diffusion coefficient of cuprous ion and double layer capacitance. The rate constants were calculated with respect to E Cu 2 + Cu 0 0 as: k 1 0 = 6.50 × 10 −5 cm s −1, k 2 0 = 0.139 cm s −1, k −2 0 = 1.88 × 10 −7 mol cm −2 s −1.