Effect of water on the electrodeposition of copper on nickel in deep eutectic solvents

Abstract

Most studies of metal electrodeposition in ionic liquids dry the electrolyte thoroughly, as water is thought to be detrimental. In some cases, water has a beneficial effect on deposit morphology.The electrodeposition of copper has been studied in 1ChCl: 2EG-water mixtures. It is shown here that the presence of water increases the apparent brightness of the deposit due to changes in the electrodeposit surface feature size, up to a water content of approximately 20 wt%. This study characterises speciation and mass transport in solution, and shows that diffusion can be controlled independently of speciation. It is shown that there is an optimal water content, which is thought to originate from formation of a bicontinuous microemulsion phase in DES-water mixtures. Additionally, the copper species remains in a predominantly ionic medium at low water content but moves to an aqueous environment when water is the main component.

23Na NMR T1 relaxation measurements as a probe for diffusion and dynamics of sodium ions in salt–glycerol mixtures

“…This has the potential to form a non-homogeneous phase as was found for water mixtures with choline-chloride based DESs. [38][39][40] Na2B4O7 . 10H2O is the only mixture with glycerol that results in a significant increase in free volume compared to pure glycerol.…”

Mechanism of selective gold extraction from multi-metal chloride solutions by electrodeposition-redox replacement

“…Although the chloride content in 1 : 2 ChCl : EG is similar to that of aqueous 4.5 M NaCl solution, the speciation of metals differs due to lower concentration of available water ligands. 43 The dominant species in this case are CuCl 4 2− and AuCl 2 − , along with CuCl 2 − for monovalent copper. [44][45][46] Therefore, the reactions according to eqn (6) as well as eqn (9) and (10) can be associated to the corresponding peaks in 1 : 2 ChCl : EG solution:…”

Deep eutectics and analogues as electrolytes in batteries

“…30 The presence of controlled amount of water does not disrupt the intermolecular peculiar interactions, 31 while decreasing DES density and viscosity, with a concurrent increase in conductivity. [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.…”

“…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.…”