Anodic dissolution of aluminum and anodic passivation in [EMIm]Cl-based ionic liquids

• Published in: Electrochemistry communications 2020-06, Vol.115, p.106720, Article 106720
• Main Authors: Böttcher, Rene, Ispas, Adriana, Bund, Andreas
• Format: Article
• Language: English
• Subjects: Aluminum; Anode passivation; Ionic liquids; Soluble anode
• ISSN: 1388-2481; 1873-1902
• DOI: 10.1016/j.elecom.2020.106720

Schematic representation of the local solidification of the electrolyte: The aluminum ion concentration (left) increases due to anodic dissolution, (center) reaches the critical concentration ccrit which leads to the formation of nuclei and (right) further formation and growth of the nuclei cause a poorly conductive layer that covers the electrode surface. [Display omitted] •Dissolution of aluminum causes a local decrease in the melting point of the electrolyte.•Solidified electrolyte precipitates on the anode and forms a poorly conducting film.•Anodic passivation is caused by slow diffusion of aluminum ions.•Intense stirring improves mass transport, but does not prevent supersaturation. The anodic dissolution of aluminum in Lewis acidic ionic liquids consisting of AlCl3 and 1-ethyl-3-methylimidazolium chloride was studied using linear sweep and cyclic voltammetry, an electrochemical quartz crystal microbalance (EQCM) and chronopotentiometry at ambient temperature. Anodic passivation of the working electrode was observed in a 2:1 electrolyte while no passivation was found in a 1.5:1 electrolyte. Chronopotentiometry proves the passivation to be caused by local solidification of the electrolyte due to an increase in the aluminum concentration near the anode. EQCM data support these results.