Daskalopoulou Evangelia, Hunt Philip, Elgar Christopher E, Yang Minjun, Abbott Andrew P, Hartley Jennifer M
School of Chemistry, University of Leicester, LE1 7RH, UK.
Faraday Discuss. 2024 Oct 25;253(0):329-342. doi: 10.1039/d4fd00030g.
Deep Eutectic Solvents (DESs) have recently been shown to be part of a dense ionic fluid continuum between ionic liquids and concentrated aqueous brines. Charge transport was shown to be governed by fluidity, with no discontinuity between molar conductivity and fluidity irrespective of cation, charge density or ionic radius. By adjusting the activity of water and chloride ions, mass transport, speciation and reactivity can be altered. It has been shown that while brines provide a high chloride content at a lower viscosity than DESs, unlike DESs, brines are unable to prevent metal passivation due to their high water content. This results in the possibility to impart a level of selectivity towards metal dissolution (or passivation) when processing mixed metal materials. Forced convection can be used to avoid the issue of slow mass transport in viscous media, and the use of jets or targeted ultrasound are effective methods for overcoming this issue. High-powered ultrasound was applied to copper, cobalt, and aluminium electrodes undergoing anodic dissolution, and linear sweep voltammetry showed a linear current-voltage response at potentials anodic of the oxidation potential under sonication, with total charge passed being 5 to 134 times greater than under silent conditions. Application of ultrasound to silver and nickel electrodes displayed an initial linear current-voltage response, but the increased water content of the brines resulted in passivation. Mass transport throughout the bulk solution is governed by the forced convection imparted by the ultrasound and ionic species must only migrate across the electrical double layer. It is shown that the anodic dissolution of a range of metals classically expected to passivate, aluminium, can be significantly accelerated under insonation conditions.
深共熔溶剂（DESs）最近被证明是离子液体和浓盐水之间密集离子流体连续体的一部分。电荷传输受流动性支配，无论阳离子、电荷密度或离子半径如何，摩尔电导率和流动性之间都没有间断。通过调节水和氯离子的活性，可以改变传质、物种形成和反应活性。研究表明，虽然盐水在比DESs更低的粘度下提供高氯含量，但与DESs不同的是，盐水由于其高含水量而无法防止金属钝化。这使得在处理混合金属材料时有可能对金属溶解（或钝化）赋予一定程度的选择性。强制对流可用于避免粘性介质中传质缓慢的问题，使用射流或定向超声是克服这一问题的有效方法。将高功率超声应用于进行阳极溶解的铜、钴和铝电极，线性扫描伏安法显示在超声处理下，在氧化电位的阳极电位处有线性电流-电压响应，通过的总电荷量比在无声条件下大5至134倍。将超声应用于银和镍电极显示出初始的线性电流-电压响应，但盐水含水量的增加导致了钝化。整个本体溶液中的传质受超声施加的强制对流支配，离子物种必须仅在双电层中迁移。结果表明，在超声条件下，一系列传统上预期会钝化的金属（如铝）的阳极溶解可以显著加速。
