Effect of temperature on the mechanisms and kinetics of cobalt electronucleation and growth onto glassy carbon electrode using reline deep eutectic solvent

This paper presents insights on the thermodynamics and kinetics of the cobalt electronucleation and growth mechanisms onto glassy carbon electrode from a eutectic mixture of choline chloride and urea. The behavior of the current density transients can be described by a model capable of considering the cobalt three-dimensional nucleation and diffusion-controlled growth from metallic nuclei and the induction-time. Using the proposed model, typical kinetic parameters such as nucleation frequency A, number density of nuclei, N0, and diffusion coefficient, D, were determined at different temperatures and applied potentials. It was found that the residual water has some effects on the early stage of the Co electrodeposition, especially on the nucleation types. Thus, at low temperature it is predominant by progressive nucleation, while at high temperature it is governed by instantaneous nucleation mechanism. Furthermore, from the temperature-dependent relationship of the diffusion coefficient, the Gibbs free energy for cobalt nucleation in DES was able to be estimated. •Mechanisms and kinetics of cobalt nucleation and growth from DES were investigated.•Chemical species of DES containing Co (II) were established using UV–vis spectra.•A model comprising (3D) nucleation and growth and induction-time was proposed.•Gibbs free energy for nucleation was determined through a model fitting method.