N-doped hierarchically porous carbon derived from grape marcs for high-performance supercapacitors

In this report, cost-effective nitrogen (N) -doped porous biocarbon was fabricated from grape marcs, and it demonstrated excellent capacitance, cyclic stability and rate performance as an electrode material for supercapacitors. By using urea as N-doping agent and KOH as activator, the as-prepared carbon material possessed suitable N-doping content (2.04 at%), well-developed porous structure and large specific surface area (2221.4 m2 g−1). As is clearly evidenced by the experimental results, the introduced N-containing functional groups could not only boost the electric double-layer capacitance (EDLC), but endow the material with considerable pseudo-capacitance under acidic conditions, thus resulting in distinct capacitances of the material under different electrolytes (446.0, 345.5 and 310.0 F g−1 at 0.5 A g−1 in 1 M H2SO4, 6 M KOH and 1 M Na2SO4, respectively). Moreover, the symmetrical supercapacitor device assembled based on this material also showed excellent performance by reaching an energy density of 16.3 Wh kg−1 with the power density of 348.3 W kg−1. All the results ensure that the biomass carbon derived from grape marcs can be used as a low cost, renewable and high-performance electrode material for supercapacitors.