Effect of water on the electrodeposition of copper from a deep eutectic solvent

Abstract

This study has examined the effect of water on the electrodeposition of copper from a deep eutectic solvent (DES). Initial physiochemical measurements showed that the viscosity and resistivity of the DES decreased with added water in the range 1 -15 wt%. This reduction in viscosity resulted in an increase in the mass transfer limiting current, without narrowing the electrochemical window or altering the speciation of the copper chloro-complexes. This shows that metal deposition rates can be increased by water additions. The effect of water on the electrochemical kinetics of the Cu(I) and Cu(II) chloro-complexes was also studied. It was found that the kinetics of the Cu(I)/Cu(0) reaction is largely irreversible, while the Cu(II)/Cu(I) couple was quasi-reversible. The rate constants for Cu(II)/Cu(I) and Cu(I)/Cu(0) reactions were accelerated by water additions, although the transfer coefficients remained unchanged. The effect of increased deposition rates, electrolyte conductivity and reaction kinetics on deposit uniformity was estimated and subsequently verified by experiments. It was found that, although higher deposition rates could be achieved, the thickness of the deposit was non-uniform since the Wagner numbers remained relatively low.

Electrodeposition of ZnNi Alloys from Choline Chloride/Ethylene Glycol Deep Eutectic Solvent and Pure Ethylene Glycol for Corrosion Protection

“…On the other side, Cu deposition in 1:2 ChCl/EG is positively affected by water. Valverde et al 56 demonstrated that water increases deposition rates and electrolyte conductivity.…”

Pulse Electrodeposition of Copper in the Presence of a Corrosion Reaction

“…In the present case, the double layer charging is controlled by the kinetically slow second step: CuCl2 -+ e- Cu + 2Cl -. In a previous study 22 values of c = 0.42 and i0 = 5.7 mA cm -2 were determined for this for this reaction. Using these values and a measured double layer capacitance of Cdl = 15 F cm -2 , the charge and discharge times were estimated.…”

Deep eutectics and analogues as electrolytes in batteries

“…[32][33][34] Even if the presence of water does not appear to lead to the electrolyte decomposition, the residual water included in the DES structure should be considered, as it affects -mostly beneficially -electrodeposition, 35,36 may reduce the electrochemical potential window, alter speciation and in general complicate the reproducible performance of measurements. [37][38][39] An interesting work reported an atomic force microscope study of the interfacial nanostructure of three ChCl-based DESs (U, G, or ethylene glycol EG as HBD) at a platinum (Pt) electrode as a function of applied potential and water content. 40 Results revealed that the interfacial nanostructure increases upon addition of water up to ~40 wt%, after which it decreases.…”

“…Despite the above mentioned donwsides, DESs have been used in many electrochemical processes, 28 including metal oxide processing, 25,43,44 electropolishing, [45][46][47][48][49] and electrodeposition of metals and alloys. 16,35,36,38,39, DESs have been electrochemically characterized using redox couples such as ferrocene, 24,76 iron (III) acetylacetonate, 77 copper(II)/copper(I), 41 and other metallic ions. [78][79][80][81] Also, the electrochemistry and adsorption behavior at the interface DES-electrodes has been investigated.…”