Electrochemical supercapacitors (ECs) have increased large attention in recent years due to their faster charging and discharging process, large specific capacity, and high power density. Herein, we designed the preparation of carbon quantum dots (CQDs), and N-/S-doped CQDs, encapsulated within graphene sheets via a lemon-juice-derived sustainable route for high-performance positive electrode material in supercapacitor application. The as-prepared electrodes revealed an unusual battery-type behavior due to the presence of large number of O-/N-/S-containing functional groups within the graphitic network of the CQDs-graphene composite, which enhances the redox-active sites. The specific capacities were obtained for CQDs, N-doped, and S-doped CQDs at 284, 181, and 125 mAh/g at 1 A/g current density. The S-doped CQDs delivered 94.5% capacitance retention over 10,000 cycles with 98% Coulombic efficiency. The real-time symmetric supercapacitor was constructed using as-prepared S-doped CQDs with an operated potential window of 1.4 V. The constructed symmetric supercapacitor shows high specific capacity, energy, and power densities of 21.7 mAh/g (55.7 F/g at 1 A/g), 15.2 Wh/kg, and 700 W/kg, respectively. The outstanding electrochemical results are based on the easy formation of heteroatom doped S and N-CQDs to enhance the better electronic/ionic motion.

近年来，电化学超级电容器（ECs）由于其充放电速度快、比容量大、功率密度高等特点，引起了人们的广泛关注。在此，我们设计了碳量子点 (CQD) 和 N-/S 掺杂 CQD 的制备方法，通过柠檬汁衍生的可持续途径封装在石墨烯片中，用于超级电容器应用中的高性能正极材料。由于在 CQDs-石墨烯复合材料的石墨网络中存在大量含 O-/N-/S 的官能团，所制备的电极显示出一种不寻常的电池类型行为，这增强了氧化还原活性位点。在 1 A/g 电流密度下，获得了 CQD、N 掺杂和 S 掺杂 CQD 在 284、181 和 125 mAh/g 下的比容量。掺杂 S 的 CQD 交付了 94 个。5% 的电容保持率超过 10,000 次循环，库仑效率为 98%。实时对称超级电容器是使用所制备的 S 掺杂 CQD 构建的，其工作电位窗口为 1.4 V。构建的对称超级电容器具有 21.7 mAh/g 的高比容量、能量和功率密度（55.7 F/g at 1 A/g)、15.2 Wh/kg 和 700 W/kg。出色的电化学结果是基于容易形成杂原子掺杂的 S 和 N-CQD 以增强更好的电子/离子运动。和 700 W/kg，分别。出色的电化学结果是基于容易形成杂原子掺杂的 S 和 N-CQD 以增强更好的电子/离子运动。和 700 W/kg，分别。出色的电化学结果是基于容易形成杂原子掺杂的 S 和 N-CQD 以增强更好的电子/离子运动。