Electrodeposition of nano- and microcrystalline aluminium in three different air and water stable ionic liquids

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-methyl-pyrrolidinium-bis(trifluoromethylsulfonyl)imide ([EMIm] Tf2N), and trihexy-tetradecyl-phosphoniumbis (trifluoromethylsulfonyl)-imide (P-14,P-6,P-6,P-6 Tf2N). The ionic liquids [BMP]Tf2N and [EMIm]Tf2N show biphasic behaviour in the AlCl3 concentration range from 1.6 to 2.5 mol/L-1, respectively. The biphasic mixtures become monophasic at temperatures >= 80 degrees C. It was found that nanocrystalline aluminum can be electrodeposited in the ionic liquid [BMP]Tf2N saturated with AlCl3. 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]Tf2N. 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-tetra-decyl-phosphonium] Tf2N at room temperature. At 150 degrees C average grain size is found to be 35 nm.