Analytical Science Group, Samsung Advanced Institute of Technology , Suwon, Gyeonggi 16678, Korea.
Energy Lab, Samsung Advanced Institute of Technology , Suwon, Gyeonggi 16678, Korea.
ACS Appl Mater Interfaces. 2018 Feb 21;10(7):6207-6217. doi: 10.1021/acsami.7b14609. Epub 2018 Feb 12.
In capacitive deionization, the salt-adsorption capacity of the electrode is critical for the efficient softening of brackish water. To improve the water-deionization capacity, the carbon electrode surface is modified with ion-exchange resins. Herein, we introduce the encapsulation of zwitterionic polymers over activated carbon to provide a resistant barrier that stabilizes the structure of electrode during electrochemical performance and enhances the capacitive deionization efficiency. Compared to conventional activated carbon, the surface-modified activated carbon exhibits significantly enhanced capacitive deionization, with a salt adsorption capacity of ∼2.0 × 10 mg/mL and a minimum conductivity of ∼43 μS/cm in the alkali-metal ions solution. Encapsulating the activated-carbon surface increased the number of ions adsorption sites and the surface area of the electrode, which improved the charge separation and deionization efficiency. In addition, the coating layer suppresses side reactions between the electrode and electrolyte, thus providing a stable cyclability. Our experimental findings suggest that the well-distributed coating layer leads to a synergistic effect on the enhanced electrochemical performance. In addition, density functional theory calculation reveals that a favorable binding affinity exists between the alkali-metal ion and zwitterionic polymer, which supports the preferable salt ions adsorption on the coating layer. The results provide useful information for designing more efficient capacitive-deionization electrodes that require high electrochemical stability.
在电容去离子过程中，电极的盐吸附能力对于有效软化咸水至关重要。为了提高水去离子能力，对碳电极表面进行了离子交换树脂改性。本文介绍了在活性炭上包覆两性离子聚合物，提供了一个稳定的阻挡层，在电化学性能过程中稳定电极结构，并提高电容去离子效率。与传统活性炭相比，表面改性后的活性炭表现出显著增强的电容去离子性能，在碱金属离子溶液中的盐吸附容量约为 2.0×10mg/mL，最小电导率约为 43μS/cm。包覆活性炭表面增加了离子吸附位点的数量和电极的表面积，从而提高了电荷分离和去离子效率。此外，涂层抑制了电极和电解质之间的副反应，从而提供了稳定的循环性能。我们的实验结果表明，均匀分布的涂层层对增强的电化学性能具有协同效应。此外，密度泛函理论计算表明，碱金属离子与两性离子聚合物之间存在有利的结合亲和力，这支持了涂层上更好的盐离子吸附。研究结果为设计需要高电化学稳定性的更高效电容去离子电极提供了有用的信息。
