酸性AlCl3-BMIC离子液体中的铝阳极溶解

采用线性扫描伏安法研究了Lewis 酸性AlCl₃-BMIC (BMIC: 1-butyl-3-methylimidazolium chloride)离子液体中铝电极的溶解. 铝电极在阳极极化时出现了钝化现象, 钝化是由于在铝电极表面形成了固体AlCl₃钝化膜造成的. 铝的电化学溶解过程可以依次分为三个区: 电化学控制区、过渡区和钝化区. 在电化学控制区, 铝的电化学溶解速率随着电位的正移而逐渐增加; 在过渡区, 由于电极表面AlCl₄^-和Al₂Cl₇^-浓度发生改变而析出固体AlCl₃使得铝电化学溶解速率随着电位的正移而逐渐减小; 当钝化膜形成之后, 铝的电化学溶解速率不再随着电位的正移而发生改变, 铝溶解进入钝化区. 增加搅拌、升高温度、降低离子液体AlCl₃摩尔分数都可以增加铝溶解阳极极限电流密度.

Dissolution Process of an Aluminum Anode in Acidic AlCl3-BMIC Ionic Liquid

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.