Advances in Copper Electrodeposition in Chloride Excess. A Theoretical and Experimental Approach

This is an in depth study in the knowledge of the nucleation and growth mechanism that governs copper electrodeposition in excess chloride media. In these conditions copper electro-reduction takes place via two well-separated steps, since the Cu(I) intermediate is stabilized through chloride complexation. The process was studied in two media, a deep eutectic solvent (DES) based on a mixture of urea and choline chloride, and in excess chloride aqueous solution, in order to also analyse solvent influence on the early stages of the deposition process. In both media, copper electrodeposition follows a nucleation and a diffusion controlled three-dimensional growth mechanism. In line with a previous work a double potentiostatic step signal was employed to record j–t transients associated to both nucleation and growth stages, and from them, the whole mechanistic analysis of the copper electrodeposition was performed. This analysis involved the calculation of the surface concentrations of Cu(II), free Cu(I) and complexed Cu(I) for any time and potential required and the application of Sharifker-Hills model, jm2tm products and rising part analysis including the calculated parameters, which are strengthened as valuable tools for complete copper electrodeposition analysis in these media.