Experimental and modeling analysis of the formation of cuprous intermediate species formed during the copper deposition on a rotating disk electrode

Two comprehensive kinetic models reported in the literature for the copper deposition in sulfate media are modeled and compared with experimental data (linear sweep voltammetry) in order to disclose the role and phase of the cuprous species as intermediates. Differences in the phase of these species are considered for each model, i.e. Cu(I)_ads and Cu⁺. Modeling considers the formation of copper in two mono-electronic steps and account for mass transport by diffusion and convection in a RDE. Reasonable fits were obtained for both models at different experimental conditions (e.g. Cu²⁺ bulk concentration, rotation rate). It was found that this behavior is possible due to the low concentrations of cuprous species and their rapid consumption to form metallic copper, i.e. not rate-controlling step. Further insights of the kinetic and mass transport contributions of this system were obtained for both models by computing some variables that cannot be experimentally measured (i.e. surface concentrations). The first reaction in the mechanism was found to be the rate-determining step. A set of optimum kinetic parameters and constants obtained from the analysis of the models are also reported in this study.