Layered Na_xCoO₂ (NCO) has been demonstrated as a promising candidate for highly efficient capacitive deionization (CDI). To further improve the desalination performance of NCO, we have developed a facile method to prepare polygon-like 3D NaCoO₂ and Na_0.6CoO₂ nanostructures employing ZIF-67 as a template for enhanced CDI. On the basis of electrochemical measurements, the 3D Na_0.6CoO₂ electrode shows a higher specific capacitance and conductivity than 3D NaCoO₂, implying better CDI performance. As a result, the salt removal capacity of 3D Na_0.6CoO₂ is 64.48 mg g⁻¹ in NaCl solution with an initial conductivity of 2000 μS cm⁻¹ and cell voltage of 1.2 V. Moreover, the desalination mechanism of 3D Na_0.6CoO₂ electrode is proposed by taking cyclic voltammetry measurements and ex situ X-ray diffraction into account, realizing the transformation from Na-rich to Na-lean during the desalination. Besides, benefiting from the novel 3D architecture, the long cyclic desalination performance of 3D Na_0.6CoO₂ electrode is much superior to that of 2D NCO. Thus, this work highlights the significance of the 3D spatial structure on the CDI performance enabled by sodium layered oxides.

中文翻译：

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用于增强电容去离子的3D NaxCoO2纳米结构工程：性能和机理

层状Na _x CoO ₂（NCO）已被证明是高效电容去离子（CDI）的有前途的候选者。为了进一步提高NCO的脱盐性能，我们开发了一种简便的方法，以ZIF-67作为增强CDI的模板制备多边形3D NaCoO ₂和Na _0.6 CoO ₂纳米结构。根据电化学测量，3D Na _0.6 CoO ₂电极比3D NaCoO ₂表现出更高的比电容和电导率，这意味着更好的CDI性能。结果，3D Na _0.6 CoO ₂的除盐能力为64.48 mg g ^-1在初始电导率为2000μScm ^-1且电池电压为1.2 V的NaCl溶液中。此外，通过循环伏安法测量和非原位X射线衍射，提出了3D Na _0.6 CoO ₂电极的脱盐机理，在脱盐过程中从富钠向贫钠的转变。此外，得益于新颖的3D体系结构，3D Na _0.6 CoO ₂电极的长循环脱盐性能远远优于2D NCO。因此，这项工作强调了3D空间结构对钠层氧化物实现的CDI性能的重要性。