Abstract
The present work shows, for the first time, a comparative experimental study on the electrodeposition of aluminium in three different water and air stable ionic liquids, namely 1‐butyl‐1‐methylpyrrolidinium‐bis(trifluoromethylsulfonyl)imide ([BMP]Tf~2~N), 1‐ethyl‐3‐methylimidazolium‐bis(trifluoromethylsulfonyl)imide ([EMIm] Tf~2~N), and trihexyl‐tetradecyl‐phosphoniumbis(trifluoromethylsulfonyl)imide (P~14,6,6,6~ Tf~2~N). The ionic liquids [BMP]Tf~2~N and [EMIm]Tf~2~N show biphasic behaviour in the AlCl~3~ concentration range from 1.6 to 2.5 mol L^−1^ and 2.5 to 5 mol L^−1^, respectively. The biphasic mixtures become monophasic at temperatures ≥80 °C. It was found that nanocrystalline aluminium can be electrodeposited in the ionic liquid [BMP]Tf~2~N saturated with AlCl~3~. The deposits obtained are generally uniform, dense, shining, and adherent with very fine crystallites in the nanometer size regime. However, coarse cubic‐shaped aluminium particles in the micrometer range are obtained in the ionic liquid [EMIm]Tf~2~N. In this liquid the particle size significantly increases as the temperature rises. A very thin, mirrorlike aluminium film containing very fine crystallites of about 20 nm is obtained in the ionic liquid [trihexyl‐tetradecyl‐phosphonium]Tf~2~N at room temperature. At 150 °C, the average grain size is found to be 35 nm.