Torkamanzadeh Mohammad, Wang Lei, Zhang Yuan, Budak Öznil, Srimuk Pattarachai, Presser Volker
INM - Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbrücken, Germany.
Department of Materials Science & Engineering, Saarland University, Campus D2 2, 66123 Saarbrücken, Germany.
ACS Appl Mater Interfaces. 2020 Jun 10;12(23):26013-26025. doi: 10.1021/acsami.0c05975. Epub 2020 May 27.
Two-dimensional, layered transition metal carbides (MXenes) are an intriguing class of intercalation-type electrodes for electrochemical applications. The ability for preferred counterion uptake qualifies MXenes as an attractive material for electrochemical desalination. Our work explores TiCT-MXene paired with activated carbon in such a way that both electrodes operate in an optimized potential range. This is accomplished by electrode mass balancing and control over the cell voltage. Thereby, we enable effective remediation of saline media with low (brackish) and high (seawater-like) ionic strength by using 20 and 600 mM aqueous NaCl solutions. It is shown that MXene/activated-carbon asymmetric cell design capitalizes on the permselective behavior of MXene in sodium removal, which in turn forces carbon to mirror the same behavior in the removal of chloride ions. This has minimized the notorious co-ion desorption of carbon in highly saline media (600 mM NaCl) and boosted the charge efficiency from 4% in a symmetric activated-carbon/activated-carbon cell to 85% in a membrane-less asymmetric MXene/activated-carbon cell. Stable electrochemical performance for up to 100 cycles is demonstrated, yielding average desalination capacities of 8 and 12 mg/g, respectively, for membrane-less MXene/activated-carbon cells in NaCl solutions of 600 mM (seawater-level) and 20 mM (brackish-water-level). In the case of the 20 mM NaCl solutions, surprising charge efficiency values of over 100% have been obtained, which is attributed to the role of MXene interlayer surface charges.
二维层状过渡金属碳化物（MXenes）是一类用于电化学应用的有趣的插层型电极。优先摄取抗衡离子的能力使MXenes成为电化学脱盐的有吸引力的材料。我们的工作探索了TiCT-MXene与活性炭的配对方式，使两个电极都能在优化的电位范围内运行。这是通过电极质量平衡和对电池电压的控制来实现的。因此，我们通过使用20 mM和600 mM的NaCl水溶液，实现了对低（微咸水）和高（海水样）离子强度的盐介质的有效修复。结果表明，MXene/活性炭不对称电池设计利用了MXene在钠去除中的选择性渗透行为，这反过来又迫使碳在去除氯离子时表现出相同的行为。这最大限度地减少了高盐介质（600 mM NaCl）中碳臭名昭著的共离子解吸，并将电荷效率从对称活性炭/活性炭电池中的4%提高到无膜不对称MXene/活性炭电池中的85%。证明了高达100次循环的稳定电化学性能，对于600 mM（海水水平）和20 mM（微咸水水平）的NaCl溶液中的无膜MXene/活性炭电池，平均脱盐容量分别为8和12 mg/g。在20 mM NaCl溶液的情况下，获得了超过100%的惊人电荷效率值，这归因于MXene层间表面电荷的作用。
