Assessment of Choline-Chloride based Ionic Liquids for Metal Deposition Seminar

Electrodeposition from ionic liquids have been heralded as the sustainable option to plating processes which require corrosive or toxic chemicals. At Newcastle we are testing the potential of ionic liquids (more precisely deep eutectic solvents, DES’s) for their potential to replace aqueous based plating operations. We have used a typical DES to plate copper, tin, and copper-tin alloys. In this presentation we will show the results obtained for copper deposition, and use it as an example to determine the issues which require resolution for its industrial use.

Cu electroplating was carried out using a pure ethaline melt, a 1:2 ratio of choline chloride and ethylene glycol, at room temperature by potentiostatic and galvanostatic methods. Hydrated cupric chloride, which is usually used in industry, was added to the pure ethaline melt. Polarisation data for cupric ion reduction to copper was collected using an RDE to determine where metal deposition was feasible. XRD analysis of the deposit showed a polycrystalline face centered cubic structure with (111) texture. The crystalline size was 66±10 nm with some internal strain. EDX analysis showed the presence of carbon and chlorine with copper in the deposit, which was due to the break-down of the DES.
Several deposition processes were carried out from a single bath to examine bath stability. The bath was found to be stable when a soluble anode was employed, and became unstable when an insoluble anode was used due to other reactions proceeding at the cathode. Plating rates for copper deposition were compared against those for aqueous systems. In addition, the cost and availability of the DES was set against that of water-based electrolytes to determine if such processes could provide economical solution.