• Izgorodina, Ekaterina I.
• Forsyth, Maria
• Macfarlane, Doug
• Bond, Alan
• Horne, Mike
• Rocher, Nathalie M.
• Rodopoulos, Theo

Abstract

Aluminium production by the high temperature (~960 °C) Hall-Heroult process is a major contributor to Australia’s economy and accounts for approximately 15% of Australia’s electricity consumption. With the advent of air, water and electrochemically stable low temperature molten salts (Ionic Liquids) an opportunity presented itself whereby aluminium could be electrodeposited via a less energy intensive lower temperatures (<100 °C) process. The feasibility of reducing aluminium chloride (AlCl3) to aluminium metal has recently been demonstrated from several ionic liquids, all of which contain the bis(trifluoromethylsulfonyl)imide (NTf2) anion.1The success of the electrodeposition is largely dependant on the composition of the ionic liquid, in particular the coordination ability of the anion, as concentration dependent complex equilibria are established between the added AlCl3 and newly generated aluminium species containing the [NTf2]- anion. We have investigated the complex chemistry of the [QA][NTf2]/AlCl3 system by 27Al-NMR, Raman spectroscopy and quantum chemical calculations. A range of aluminium complexes were identified such as [AlCl4]-, [Al(NTf2)3] and [AlCl3(NTf2)]-.2,3 Correlation of these data to electro-deposition data indicated that the electroactive species is likely to be 4-coordinated [AlCl3(NTf2)]-.

Topics

• impedance spectroscopy
• aluminium
• laser emission spectroscopy
• Nuclear Magnetic Resonance spectroscopy
• electrodeposition
• Raman spectroscopy