Polystyrene foam derived nitrogen-enriched porous carbon/graphene composites with high volumetric capacitances for aqueous supercapacitors

Abstract

Polystyrene (PS) foam derived nitrogen-enriched porous carbon/graphene (AC/Gr) composites were prepared using ammonia, ethylene diamine and melamine as nitrogen sources, respectively. The as-prepared AC/Gr composites and graphene-free PS-derived porous carbon (PSAC) exhibit moderate specific surface areas in a range of 915–1489 m2 g−1. Compared to PSAC, AC/Gr composites exhibit significantly improved energy storage capability, a high gravimetric capacitance of 339 F g−1 or volumetric capacitance of 365 F cm−3 was achieved at a current density of 0.05 A g−1 in 6 M KOH aqueous electrolyte. The assembled aqueous symmetric supercapacitors are capable of deliver both high energy density and high power density, for example, 11.8 W h kg−1 (12.7 W h L−1) with a power density of 12.5 W kg−1 (13.4 W L−1), and 6.2 W h kg−1 (6.7 W h L−1) with 4.6 kW kg−1 (5.0 kW L−1) for MAC/Gr-based supercapacitor.