Abstract Currently, limited charge efficiency and poor long-term desalination stability remain the major challenges for the practical application of membrane-free capacitive deionization (CDI). Hybrid capacitive deionization (HCDI) is suggested to effectively address these issues. Although cathode-hybridized HCDI has been studied widely, anode-hybridized HCDI has been seldom reported to date. In this work, a radical polymer, poly (2,2,6,6-tetramethylpiperidinyloxy methacrylate) (PTMA), with good anion-storage capability was used as the anode of the membrane-free HCDI (denoted as A-HCDI) for the first time. PTMA restrains the undesirable faradaic reactions that occur on the conventional carbon anodes and suppresses the cation expulsion effect that dominates the charging process of the carbon anode after the long-term oxidation, degrading the membrane-free CDI process. Compared with AC anode, PTMA anode improves the average charge efficiency from 18.7% to 48.6% in the first 20 cycles at 1.2 V. Moreover, A-HCDI exhibits a long-term stable salt removal capacity of 13.9 mg g−1 during charging/discharging at 1.2/0 V for 500 h, while membrane-free CDI only remains effective before 70 h. The novel A-HCDI provides a new approach for efficient and stable membrane-free electrochemical desalination.

中文翻译：

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新型无膜混合电容去离子与自由基聚合物阳极稳定脱盐

摘要 目前，有限的充电效率和较差的长期脱盐稳定性仍然是无膜电容去离子（CDI）实际应用的主要挑战。建议使用混合电容去离子 (HCDI) 来有效解决这些问题。尽管阴极杂化HCDI已被广泛研究，但迄今为止很少报道阳极杂化HCDI。在这项工作中，具有良好阴离子存储能力的自由基聚合物聚（2,2,6,6-四甲基哌啶基氧基甲基丙烯酸酯）（PTMA）用作无膜 HCDI（表示为 A-HCDI）的阳极，用于第一次。PTMA抑制了传统碳负极上发生的不良法拉第反应，并抑制了长期氧化后主导碳负极充电过程的阳离子排出效应，降解无膜 CDI 过程。与交流阳极相比，PTMA 阳极在 1.2 V 的前 20 次循环中将平均充电效率从 18.7% 提高到 48.6%。此外，A-HCDI 在充电期间表现出 13.9 mg g-1 的长期稳定脱盐能力/以 1.2/0 V 放电 500 小时，而无膜 CDI 仅在 70 小时前保持有效。新型 A-HCDI 为高效稳定的无膜电化学脱盐提供了一种新方法。