Electrodeposition of copper composites from deep eutectic solvents based on choline chloride

Abstract

Here we describe for the first time the electrolytic deposition of copper and copper composites from a solution of the metal chloride salt in either urea-choline chloride, or ethylene glycol-choline chloride based eutectics. We show that the deposition kinetics and thermodynamics are quite unlike those in aqueous solution under comparable conditions and that the copper ion complexation is also different. The mechanism of copper nucleation is studied using chronoamperometry and it is shown that progressive nucleation leads to a bright nano-structured deposit. In contrast, instantaneous nucleation, at lower concentrations of copper ions, leads to a dull deposit. This work also pioneers the use of the electrochemical quartz crystal microbalance (EQCM) to monitor both current efficiency and the inclusion of inert particulates into the copper coatings. This technique allows the first in situ quantification or particulate inclusion. It was found that the composition of composite material was strongly dependent on the amount of species suspended in solution. It was also shown that the majority of material was dragged onto the surface rather than settling on to it. The distribution of the composite material was found to be even throughout the coating. This technology is important because it facilitates deposition of bright copper coatings without co-ligands such as cyanide. The incorporation of micron-sized particulates into ionic liquids has resulted, in one case, in a decrease in viscosity. This observation is both unusual and surprising; we explain this here in terms of an increase in the free volume of the liquid and local solvent perturbation.

Electrochemistry and speciation of Au+in a deep eutectic solvent: growth and morphology of galvanic immersion coatings

“…35,42 The observed electrochemical behaviour for AuCl in Ethaline 200 is also similar to that observed for the Ag +/0 and Cu +/0 redox couples, with well-defined, chemically reversible deposition and stripping behaviour. 38,43,44 Multiple peaks are visible in the FT for the KAu(CN) 2 solution, Figure 3 (c), suggesting coordination with two cyanide ligands. This speciation is also observed for KAu(CN) 2 in both aqueous and quaternary ammonium salt solutions.…”

Anodic Reactions and the Corrosion of Copper in Deep Eutectic Solvents

“…These 'type-III' DES systems have been used to deposit a wide range of metals including Al, Zn, Fe, Ni, Sn, Cr, Al and Cu [2][3][4][5][6][7] . Studies [8][9][10][11][12][13][14] of copper deposition have been particularly common as it is used extensively in the electronics and microelectronic industries and can be regarded as a model system. Additionally there is a large body of existing studies of 4 Cu deposition from conventional ILs and aqueous systems which can be used to benchmark DES-based processes.…”

Deep Eutectic Solvents: An Overview of its Application as a “Green” Extractant

“…Owing to their physical properties, many researchers have reported that DESs have feasible industrial applications [18][19][20][21][22][23]. As reviewed by Zhang et al, [24] and Tang et al, [25], there are many potential areas to which DESs can be applied.…”