In recent years there has been considerable interest in the deposition of metals, alloys and semiconductors from ionic liquids (ILs). These melts possess a number of advantages over traditional aqueous solutions, especially for the deposition of reactive metals and where the current efficiency of the process is inherently low. Deep eutectic solvents (DES) are a new class ionic liquids which possess low toxicity, low cost, and relatively good electrochemical characteristics. They have been used to deposit a wide range of materials and, unlike traditional ILs, it is often possible to obtain acceptable deposit characteristics in the presence of significant amounts of water contamination. This makes them particularly suitable for industrial-scale plating. Until now, most studies employing ILs or DES have concentrated on DC plating and there have been relatively few reports of electrodeposition under pulse conditions.

Ionic liquids have differing characteristics to aqueous solutions, particularly in terms of their double layer structure, mass transport properties, kinetics and conductivity. These differences indicate that pulse parameters developed for aqueous systems are unlikely to be optimal for deposition from ILs. For example, the very low diffusivity of the depositing species indicates that the DC and pulse limiting current are expected to be substantially lower compared to aqueous solutions. In this paper we will examine some of the constraints placed on the selection of pulse parameters dictated by the unusual properties of ionic liquids.

As an example of a ‘model’ system we will examine copper deposition from a deep eutectic solvent (DES) comprising ethylene glycol and choline chloride. After selection of appropriate pulse parameters some preliminary results obtained for copper electrodeposition will be reported. Of particular importance is the presence of a corrosion reaction in the off-time which puts additional constraints on the choice of pulse parameters.