N/S co-doped coal-based porous carbon spheres as electrode materials for high performance supercapacitors.

N/S co-doped porous carbon spheres (NSPCSs) were prepared by a simple ultrasonic spray pyrolysis (USP) using the mixed solution of coal oxide and l-cysteine, and without a subsequent activation process. The surface properties of carbon materials have been successfully modified by the concurrent incorporation of N and S. So the capacitive performance of NSPCSs was greatly enhanced. It is used as a supercapacitor electrode to achieve a high specific capacitance of 308 F g at a current density of 1 A g and 90.2% capacitance retention even after 10 000 cycles at 5 A g. These numerical results show that the supercapacitors based on coal-based carbon materials have great potential in high performance electrochemical energy storage.