Abstract Nitrogen-doped activated carbon (NAC) is prepared by a combination of acid pre-treatment and thermal nitrogen doping for the positive electrode of asymmetric capacitive deionization (a-CDI) cells. The oxygen content in AC controlled by the acid pre-treatment significantly affects the doping amount of N atoms from melamine, which enhances the surface negative charge in NACs to promote the salt adsorption capacity (SAC). Here NAC with 30% HNO3 pre-treatment (NAC30) possesses a highly negatively charged surface to exhibit a fast ion desorption rate during discharging. The asymmetrical NAC30//AC cell shows the maximum reversible SAC of 24.7 ± 1.6 mg g−1. In addition, the negative surface charge of NAC30 is further promoted and the reversible SAC of NAC30//AC are greatly enhanced to ca. 55 mg g−1 when pH of the 8 mM NaCl solution is adjusted from 5.4 to 7.5. In the long-term stability test, NAC30//AC remains 40% of its maximum reversible SAC after 100 charging-discharging cycles, indicating that our nitrogen doping is able to effectively reduce the oxidation of activated carbon, confirmed by the electrochemical impedance analysis.

中文翻译：

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用于电容去离子的掺氮活性炭的改进性能和长期稳定性

摘要 掺氮活性炭（NAC）是通过酸预处理和热氮掺杂相结合的方法制备的，用于非对称电容去离子（a-CDI）电池的正极。酸预处理控制的活性炭中的氧含量显着影响三聚氰胺中 N 原子的掺杂量，这增强了 NAC 中的表面负电荷以促进盐吸附能力（SAC）。此处采用 30% HNO3 预处理的 NAC (NAC30) 具有高度带负电荷的表面，在放电过程中表现出快速的离子解吸速率。不对称 NAC30//AC 电池的最大可逆 SAC 为 24.7 ± 1.6 mg g-1。此外，进一步促进了 NAC30 的表面负电荷，NAC30//AC 的可逆 SAC 大大增强至约。当 8 mM NaCl 溶液的 pH 值从 5.4 调整到 7.5 时，为 55 mg g-1。在长期稳定性测试中，NAC30//AC在100次充放电循环后仍保持其最大可逆SAC的40%，表明我们的氮掺杂能够有效减少活性炭的氧化，电化学阻抗分析证实。