Although capacitive deionization (CDI) is an energy-efficient and environment-friendly desalination technique, the severe performance decrease during long-term operation has been a critical obstacle to its practical application. Compared to various other approaches for stability improvement, the ion-exchange polymer (IEP) coating on the electrode seems to be both efficient and economically feasible. Nevertheless, there have only been limited studies aimed at understanding the role of IEP on stabilizing CDI operations. In this study, we investigated the effect of IEP on CDI performance by varying the amount of IEP coated on the electrodes. The polymer layer thickness was varied across the three IEP-coated electrodes used in this study (0, 30, and 100 μm). By monitoring the salt adsorption capacity (SAC) during the 50-h operation, it was found that the long-term stability of the system was dramatically improved upon using the IEP-coated electrodes. Additionally, the SAC retention was further improved with increasing IEP layer thickness. Based on the experimental analysis, we could conclude that the activated carbon particles’ coating layer acted as a barrier to block the water molecules from the electrode surface, hence impeding carbon oxidation. The outer polymer layer formed on the electrode could additionally block the diffusion of oxygen sources from the bulk solution to the electrode, which further reduced the possibility of carbon oxidation. The results suggest that the IEP coating is effective towards maintaining the performance of the electrodes, and thicker IEP layers increased the electrode stability.

中文翻译：

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使用涂有离子交换聚合物的活性炭电极评估电容去离子的长期稳定性

尽管电容去离子（CDI）是一种节能环保的海水淡化技术，但长期运行期间性能的严重下降一直是其实际应用的关键障碍。与其他各种提高稳定性的方法相比，电极上的离子交换聚合物 (IEP) 涂层似乎既有效又经济可行。然而，只有有限的研究旨在了解 IEP 在稳定 CDI 运营方面的作用。在这项研究中，我们通过改变涂覆在电极上的 IEP 量来研究 IEP 对 CDI 性能的影响。本研究中使用的三个 IEP 涂层电极的聚合物层厚度不同（0、30 和 100 μm）。通过监测 50 小时运行期间的盐吸附容量 (SAC)，发现使用 IEP 涂层电极后系统的长期稳定性得到显着改善。此外，随着 IEP 层厚度的增加，SAC 保留率进一步提高。根据实验分析，我们可以得出结论，活性炭颗粒的涂层充当屏障，阻止水分子从电极表面进入，从而阻止碳氧化。在电极上形成的外聚合物层可以额外阻止氧源从本体溶液扩散到电极，这进一步降低了碳氧化的可能性。结果表明，IEP 涂层对于保持电极的性能是有效的，并且更厚的 IEP 层增加了电极的稳定性。