Hierarchical porous carbon spheres constructed from coal as electrode materials for high performance supercapacitors

Hierarchical porous carbon spheres (PCS) are prepared by a simple one-pot spray pyrolysis of coal oxide solution without any further activation process. The specific surface area and total pore volume of the resultant carbon spheres are increased significantly with the increase of spray pyrolysis temperature. When evaluated as electrode materials for supercapacitors in 6 M KOH electrolyte, the PCS exhibits a high specific capacitance 227 F g(-1) at a current density of 1 A g(-1) and outstanding cycling stability after 10 000 charge/discharge cycles at a current density of 2 A g(-1). In symmetric supercapacitor, the specific capacitance of the sample PCS-8 is 180 F g(-1) at a current density of 0.2 A g(-1) and has excellent rate capability. The proposed strategy offers a facile and green method to produce porous carbon spheres from coal, and has potential application in energy storage.