Electrodeposition of Al from a 1-butylpyrrolidine-AlCl₃ ionic liquid

Abstract

The addition of 1-butylpyrrolidine to AlCl₃ results in the formation of an electrolyte that is suited to Al deposition. The feasibility of electrodepositing Al from the synthesized electrolyte was investigated. Several compositions of AlCl₃ and 1-butylpyrrolidine were prepared for this purpose. These mixtures show a different phase behavior at various compositions of AlCl₃ and 1-butylpyrrolidine. IR, Raman and NMR spectroscopy were employed to characterize the synthesized liquids. Among the prepared compositions, 1:1.2 mol ratio of 1-butylpyrrolidine:AlCl₃ and the upper phase of 1:1.3 mol ratio of 1-butylpyrrolidine:AlCl₃ were found to be suitable for Al electrodeposition at room temperature (RT). Uniform and thick (~µm thick) layers of Al were obtained on copper at RT. Al deposition occured from the cationic species of ${\mathrm{AlCl}}_{3-x}{\mathrm{L}}_y^{+}$ (where $x\le 2$, y=1–2, and L=1-butylpyrrolidine) in this electrolyte. This behavior is contrary to the well investigated classic AlCl₃ based ionic liquids, where the deposition of Al occurs mainly from anionic ${\mathrm{Al}}_2{\mathrm{Cl}}_7^{-}$ ions.