N/O Co-doped Porous Carbons Derived from Coal Tar\nPitch for Ultra-high Specific Capacitance Supercapacitors

Abstract

In this paper, a\nseries of N/O co-doped porous carbons (PCs) were\ndesigned and used to prepare coal tar pitch-based supercapacitors\n(SCs). The introduction of N/O species under the intervention of urea\neffectively improves the pseudocapacitance of PCs. The results show\nthat the specific surface area of synthesized N₃PC_4‑700 is 1914 m² g^–1, while\nthe N and O contents are 1.3 and 7.2%, respectively. The unique interconnected\npore structure and proper organic N/O co-doping, especially the introduction\nof pyridine-N and pyrrole-N, are beneficial for improving the electrochemical\nperformance of PCs. In the three-electrode system, the specific capacitance\nand rate capability of N₃PC_4‑700 are\n532.5 F g^–1 and 72.5% at the current densities of\n0.5 and 20 A g^–1, respectively. In addition, the\nspecific capacitance of N₃PC_4‑700 in\na coin-type symmetric device is 315.5 F g^–1 at 0.5\nA g^–1. The N₃PC_4‑700 electrode provides an energy density of 43.8 W h kg^–1 with a power density of 0.5 kW kg^–1 and still\nmaintains a value of 29.7 at 10 kW kg^–1. After 10,000\ncharge/discharge cycles, the retention rate was as high as 96.7%.\nIn order to obtain high-performance carbon-based SCs, the effective\nidentification and regulation of organic N/O species is necessary.