Diffusion Coefficients and Kinetic Parameters in Copper Sulfate Electrolytes and in Copper Fluoborate Electrolytes Containing Organic Addition Agents

Abstract

Measured limiting currents iL for the deposition of copper on a platinum rotated disk electrode (RDE) were used to calculate the diffusion coefficients of copper ions in high‐purity aqueous copper sulfate and copper fluoborate electrolytes. The diffusion coefficient in a electrolyte was found to be , while the diffusion coefficient in a electrolyte was found to be . The values of iL were found to be directly proportional to the square root of the disk rotational rate ω, as predicted by theory. Consistent correlations between the kinetic parameters controlling copper depositions and the concentration of addition agents were found for copper fluoborate electrolytes containing Cubath Hy,1 thiourea, and gelatin. Generally both the transfer coefficients (αc) and the exchange current densities (io) were found to decrease with increasing concentrations of additives, in accord with the hypothesis that additives retard primary charge transfer and the rate of copper deposition. Anomalous results were obtained at a thiourea concentration of and at a gelatin concentration of .