Dissolution process of an aluminum anode in acidic AlCl3-BMIC ionic liquid

Abstract

The dissolution process of an aluminum electrode in Lewis acidic ionic liquid aluminum chloride (AlCl3)-1-butyl-3-methylimidazolium chloride (BMIC) was studied using linear sweep voltammetry. Passivation was observed upon anodic polarization of the aluminum electrode that was caused by formation of a solid AlCl3 layer on the surface of the aluminum electrode. The electrochemical dissolution process of aluminum can be divided into electrochemically-controlled, transition, and passivation regimes. In the electrochemically-controlled regime, the dissolution rate of aluminum increased with increasing potential. In the transition regime, the dissolution rate of aluminum decreased as the potential increased because of the formation of solid AlCl3 caused by changes in the concentration of AlCl4 - and Al2Cl7 -. After a passivation layer formed, the dissolution rate of aluminum depended on the diffusion of AlCl4 - was independent of potential; that is, the electrochemical dissolution process entered the passivation regime. The anodic limiting current density increased with agitation, increasing temperature, and decreasing mole fraction of AlCl3 in the ionic liquid. © Editorial office of Acta Physico-Chimica Sinica.