Direct synthesis of 3D hollow porous graphene balls from coal tar pitch for high performance supercapacitors

3D hollow porous graphene balls (HPGBs) were synthesized directly from coal tar pitch for the first time by a simple nano-MgO template strategy coupled with KOH activation. The as-made HPGBs feature a 3D spherical architecture with a thin porous shell that has a high specific surface area and consists of macropores, mesopores and micropores in a well-balanced ratio. As the electrode material for supercapacitors, the as-made HPGBs show a high specific capacitance of 321 F g(-1) at 0.05 A g(-1), an excellent rate performance of 244 F g(-1) at 20 A g(-1), and good cycle stability with over 94.4% capacitance retention after 1000 cycles. This work may pave a new way for efficient and scaled-up production of low-cost spherical graphene materials, from aromatic hydrocarbon sources such as coal tar and heavy oils, for supercapacitors.