AlCl_3-BMIC离子液体中Na^+含量对铝电沉积的影响

Effect of Na^+ content on electrodeposition of aluminum from AlCl^3-BMIC ionic liquid

测定AlCl3-BMIC离子液体(摩尔比2:1)电导率与Na+含量的关系,采用循环伏安法研究不同Na+含量离子液体的电化学性能,并通过恒电流电沉积考察Na+含量对槽电压、电流效率、沉积层形貌及电沉积铝纯度的影响。结果表明:随着Na+含量增加,离子液体的电导率和铝电还原峰值电流密度降低,交换电流密度增加,传递系数基本保持不变;而且铝沉积的电流效率降低、能耗增加。此外,当离子液体中Na+含量低于0.2 g/L时,对铝沉积层形貌影响不大,当Na+含量增加到0.5 g/L时,沉积层变得平整致密,颗粒减小,但进一步增加Na+含量,颗粒又逐渐长大。离子液体中Na+的存在对铝沉积层的纯度影响很小,即使Na+含量高达2.0 g/L,铝沉积层中Na含量也非常低。

The electrical conductivities of AlCl 3-BMIC（mole ratio of AlCl 3 to BMIC being 2：1） ionic liquids were measured as a function of the Na＋ content.The effect of Na＋ content on electrochemical characteristics of ionic liquid was investigated by the cyclic voltammetry.Constant current deposition experiments were used to study the effect of Na＋ content on the cell voltage,current efficiency,surface morphology and purity of aluminum electrodeposits.The results show that the electrical conductivities of ionic liquid and the cathodic peak current density decrease,the exchange current density increases,and the transfer coefficient basically remains unchanged with the increase of Na＋ content in the ionic liquid.Constant current deposition experiments show that the current efficiency decreases and the energy consumption increases with the increase of Na＋ content.The presence of Na＋ only has minimal effect on the surface morphology of the aluminum deposits when Na＋ content is below 0.2 g/L.Aluminum deposits become more compact,and the grain size decreases as the Na＋ content increases up to 0.5 g/L,but further increasing Na＋ content,aluminum deposits are still compact,but the grain size increases.The purity of aluminum deposits is not virtually affected by Na＋ content in ionic liquid electrolytes.The Na content of the aluminum deposits is very low even though the Na＋ content is up to 2 g/L.