Nitrogen-doped coal-based microporous carbon material co-activated by HCOOK and urea for high performance supercapacitors

The doping of heteroatoms can adjust the surface chemical state of porous carbons, which is conducive to improving the surface activity, and enhancing the hydrophicity and conductivity of carbon electrodes. Herein, we developed a facile and green strategy to obtain nitrogen-doped coal-derived porous carbon dominated by micropores for high performance supercapacitor. The hydrothermal treatment of coal and urea can not only achieve the doping of nitrogen atoms, but also conducive to the subsequent activation process. Benefiting from the large micropore volume and specific surface area (0.68 cm3 g-1 and 1563 m2 g-1), suitable micropore size, and high content of surface C--O, N-Q and N-5, the optimal sample exhibits a large capacitance of 371 F g-1 (1 A g-1), high capacitance retention of 67% (50 A g-1), and outstanding cyclic durability in a three-electrode system (aqueous electrolyte). Furthermore, the symmetrical supercapacitor in neat EMIM BF4 shows a high energy density of 40 Wh kg- 1 (625 W kg- 1). This work proposes a facile and potential strategy for preparing nitrogendoped porous carbon materials with outstanding electrochemical property for supercapacitors and provides a novel insight for the efficient and low carbonization utilization of coal resources.