On Wetting Angles and Nucleation Energies during the Electrochemical Nucleation of Cobalt onto Glassy Carbon from a Deep Eutectic Solvent

Abstract

This work deals with the electrochemical nucleation of cobalt, onto a glassy carbon electrode, from a deep eutectic solvent formed by choline chloride and urea in a 1:2 molar ratio. The nucleation mechanism was studied through electrochemical techniques. From the analysis of the experimental potentiostatic current transients, the kinetic parameters such as the nucleation frequency, A, and the number density of active sites, N0, were determined. In this work, A was also expressed as a function of the wetting angle, θ, (A(θ)) where the local distribution of θ was calculated through a stochastic simulation of the misorientation angle distribution derived from a created random texture. The A(θ) obtained from such a stochastic approach was in good agreement with the experimental data thus leading to determination of the Gibbs free energy of nucleation ΔG(nc) and the critical nucleus size nc, aside from other kinetic parameters such as the transfer coefficient α, the exchange current density j0, and the surface tension σ. Furthermore, a new method of calculating the nucleation energy from a voltammetric trace recorded during cobalt nucleation onto glassy carbon was proposed and validated. This method provides a novel tool to assess the experimental magnitude and to measure the nucleation energy.