▎ 摘　　要

Doping with heteroatoms has become an approach for improving the electrochemical performance of few-layered graphene. In this work, Sulfur-nitrogen co-doped few-layered graphene synthesized from the graphite flakes acid treated with H2SO4 and HNO3 followed by microwave irradiation. Sulfur-nitrogen co-doped few-layered graphene consists of less than 15 graphene layers with a high degree of graphitization. The supercapacitor exhibited a specific energy density of 15 Wh kg(-1) at a power density of 300 W kg(-1) at room temperature in aqueous electrolyte. The S, N-FLG electrodes show the specific capacitance of 298 F g(-1) at a current density of 1 A g(-1) land stable over 10,000 continuous charge-discharge cycles with 95% capacitance retention at 1 A g(-1). The obtained capacitance is due to maximum utilization of few-layered graphene sheets, highest intrinsic surface capacitance due to the synergetic effect of the formation of N-S-H hydrogen bonds and S, N co-doping in graphene aromatic rings. (C) 2020 Elsevier Ltd. All rights reserved.