Electrodeposition of nanocrystalline aluminium, copper, and copper–aluminium alloys from 1-butyl-1-methylpyrrolidinium trifluoromethylsulfonate ionic liquid

Abstract

In this paper, we show that nanocrystalline aluminium, copper, and copper–aluminium alloys can be electrodeposited from the ionic liquid 1-butyl-1-methylpyrrolidinium trifluoromethylsulfonate, [Py1,4]TfO. Furthermore, Al deposition was studied in 1-ethyl-3-methylimidazolium trifluoromethylsulfonate, [EMIm]TfO for comparison. The two employed ionic liquids exhibit different concentration-dependent phase behaviour with AlCl3. This study comprises cyclic voltammetry, potentiostatic electrolysis, scanning electron microscopy, X-ray diffraction, atomic absorption spectroscopy, and inductively coupled plasma optical emission spectroscopy. Thick (in micrometre regime) and uniform layers of aluminium deposits were obtained from 2.75 M AlCl3 in [Py1,4]TfO at 100 °C. The average crystallite size of aluminium was found to be around 40 to 50 nm. However, a coarse and cubic-shaped Al deposit with crystal sizes in the micrometre regime was obtained from [EMIm]TfO. Electrodeposition of copper was investigated in [Py1,4]TfO-containing Cu(TfO)2 at 100 °C. The average grain size of the copper deposit obtained from the electrolysis is around 20 to 40 nm. Electrodeposition of copper–aluminium alloys was successful in the same ionic liquid at 100 °C. Thick layers of copper–aluminium alloys were obtained from the employed ionic liquid. XRD analysis of the obtained deposits from electrolysis experiments revealed that Cu3Al alloy was formed. SEM analysis indicated that the nanocrystalline copper–aluminium deposits have an average grain size of 60 to 70 nm.