Aluminium electrodeposition from a novel hydrophobic ionic liquid tetramethyl-guanidinium-perfluoro-3-oxa-4,5 dichloro-pentan-sulphonate

Abstract

Aluminium electrodeposition is demonstrated from a novel ionic liquid (IL), tetramethyl guanidinium -perfluoro-3-oxa-4,5 dichloro-pentan-sulphonate [C5H14N3+][CF2ClCFClOCF2CF2SO3-]. This air and water stable ionic liquid owns a strong hydrophobic nature that was conceived to allow aluminium deposition in ambient conditions. This work presents the studies performed on the electrodeposition processes and reports images regarding the surface morphology of aluminium electrodeposited on vitreous carbon from solutions having a wide range of AlCl3 : IL molar ratios. The electrochemical window of this liquid is temperature dependent and sufficiently wide to allow aluminium deposition. The conductivity of solutions is highly influenced by the AlCl3 content. Solutions that allow aluminium electrodeposition are characterized by an AlCl3 : IL molar ratio that ranges between 0.9 and 1.3. This compositional range probably represents the best compromise between Al(III) concentration and conductivity values that allow sufficient mobility of the electroactive species. Nucleation and three dimensional growth was evidenced from both voltammetric and potentiostatic experiments. Cyclic voltammograms show a significant loop and j-t transients the characteristic maximum, conventionally attributed to nucleation. Electrochemical evidences are confirmed by SEM images of the deposits, in which rounded or faceted crystals were observed depending on the electrodeposition conditions.