The combination of capacitive carbon nanomaterials with metal oxides as electrode materials for capacitive deionization (CDI) has emerged as a promising strategy for water desalination. Herein, environmentally friendly nanocomposites of nitrogen doped graphene quantum dots (N-GQDs) decorated onto halloysite nanotubes (HNTs) have been developed for enhanced CDI. The decoration of as-prepared 8–10 nm N-GQDs onto the surface of HNTs (N-GQDs@HNT) significantly reduces the electric resistance. The N-GQDs@HNT nanocomposites exhibit an ideal electric double layer feature with high specific capacitances of 335 and 201 F g⁻¹ at 0.5 and 10 A g⁻¹, respectively. In addition, more than 95% of the original capacitance can be retained after 3000 charge/discharge cycles at 1 A g⁻¹, which indicates the superior rate capability and stability of the nanocomposites. The symmetric N-GQDs@HNT electrode shows an excellent specific electrosorption (SEC) of 20.1 mg g⁻¹ (874 μmol g⁻¹) and high stability toward Na⁺ removal after 3 consecutive charge/discharge processes. The CDI Ragone plot indicates that the SEC of N-GQDs@HNT is highly dependent on the flow rate, applied voltage and initial NaCl concentration. The superior electrochemical performance of N-GQDs@HNT is mainly attributed to the increased charge storage sites and good electrical conductivity, resulting in the improvement of the charge transfer and ion transport. These superior performance features make the N-GQDs@HNT a promising electrode material which can pave the way for the development of next generation and environmentally friendly technology using naturally occurring clay minerals as high performance electrode materials for water desalination.

中文翻译：

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氮掺杂石墨烯量子点修饰的富地球纳米管，用于增强电容去离子

电容碳纳米材料与金属氧化物作为电容去离子（CDI）的电极材料的结合已成为一种有希望的水脱盐策略。在此，已经开发了装饰在埃洛石纳米管（HNT）上的氮掺杂石墨烯量子点（N-GQD）的环保纳米复合材料，用于增强的CDI。在HNT表面（N-GQDs @ HNT）上装饰准备好的8–10 nm N-GQD会大大降低电阻。N-GQDs @ HNT纳米复合材料表现出理想的双电层特征，在0.5和10 A g ^-1时分别具有335和201 F g ^-1的高比电容。此外，在1 A g ^-1下进行3000次充电/放电循环后，可以保留超过95％的原始电容，这表明纳米复合材料具有优异的速率能力和稳定性。对称的N-GQDs @ HNT电极显示出20.1 mg g ^-1（874μmolg ^-1）的优异比电吸附（SEC ）和对Na ^+的高稳定性连续3次充电/放电过程后清除。CDI Ragone图表明N-GQDs @ HNT的SEC高度依赖于流速，施加的电压和初始NaCl浓度。N-GQDs @ HNT的优异电化学性能主要归因于增加的电荷存储位点和良好的导电性，从而改善了电荷转移和离子迁移。这些优越的性能使N-GQDs @ HNT成为一种很有前途的电极材料，它可以为使用天然粘土矿物作为水脱盐的高性能电极材料的下一代环保技术的发展铺平道路。