Additive free electrodeposition of nanocrystalline aluminium in a water and air stable ionic liquid

This paper shows for the first time that nanocrystalline aluminium can be electrodeposited without any additives in the ionic liquid 1-butyl-1-methyl pyrrolidinium bis(trifluoromethylsulfonyl)imide saturated with AlCl3. The advantages of this ionic liquid compared to chloroaluminate ionic liquids, which were intensively investigated in the past, are that it is water and air stable, easy to purify as well as it is easy to dry to water contents below 1 ppm. Interestingly, this ionic liquid shows biphasic behaviour above a concentration of AlCl3 of 1.6 mol/L. A significant current loop attributed to nucleation was found for bulk deposition of aluminium at room temperature on gold, whereas at 100 °C there is no nucleation loop. The deposits obtained are generally uniform, dense, shining and adherent to the substrate with crystallites in the nanosize regime. At 100 °C, the quality of the deposit is even better with an average size of the crystallites of 34 nm.