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

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, N 0 , 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 Δ G ( n c ) and the critical nucleus size n c , aside from other kinetic parameters such as the transfer coefficient α, the exchange current density j 0 , 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.