Facile synthesis of B/N co-doped porous carbon nanosheets with high heteroatom content and electrical conductivity for excellent-performance supercapacitors

Abstract

Herein, we present a facile synthesis of B/N co-doped porous carbon nanosheets (BNMNC) from sodium-lignosulfonate-based porous carbon nanosheets based on synergistic effect of (NH4)2SO4 and B2O3. A chain co-doping mechanism of B/N heteroatoms is proposed, corresponding to the mutualpromotioneffect of B − N bonds and N-6/N-5 groups during their formation process. BNMNC simultaneously possesses high B (6 at %) and N (7.3 at %) contents, excellent electrical conductivity (1225 S m−1) and considerable specific surface area (880 m2 g−1). In two-electrode system using 3 M KOH electrolyte, BNMNC exhibits large specific capacitance of 224F g−1 at 0.25 A g−1, high capacitance retention of 81.3% at 20 A g−1, together with superior cycling stability with 96% capacitance retention after 10,000 cycles. Furthermore, BNMNC-based supercapacitor can deliver high energy densities of 7.2 and 3.9 Wh kg−1 at the power densities of 70.1 W kg−1 and 5.1 kW kg−1, respectively. Impressively, a large energy density of 58.1 Wh kg−1 at 878 W kg−1 can be achieved, which retains 13.8 Wh kg−1 even at 11.8 KW kg−1 in EMIMBF4 ionic liquid electrolyte.