One-step production of O-N-S co-doped three-dimensional hierarchical porous carbons for high-performance supercapacitors

Besides the complex and low-yield synthesis, attaining high energy density whilst maintaining high power density remains as the major challenge for supercapacitor applications. Herein, we report one-step production of O-N-S co-doped hierarchical porous carbons (HPCs) from ant powder. The resultant product possesses a large specific surface area (2650 m2 g−1), a typical three-dimensional (3-D) framework comprised of interconnected macro-, meso- and micropores with suitable pore size distribution, together with an appropriate heteroatom doping of O, N, and S. These distinct features have afforded an ultra-high specific capacitance of 576 F g−1 at a current density of 1.0 A g−1 in a three-electrode system and 352 F g−1 at a current density of 0.1 A g−1 in a two-electrode system, using 6 mol L−1 KOH aqueous as electrolyte. Moreover, the high rate retention of ∼80% from 1.0 A g−1 to 10.0 A g−1 and the high cycling stability (∼ 5% loss over 10,000 cycles) have been also demonstrated. Most importantly, the fabricated symmetric supercapacitors using 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) electrolyte delivered an energy density as high as 107 Wh kg−1 at a power density of 900 W kg−1, and a remarkable energy density of 67 Wh kg−1 can be retained even at a power density as high as 18,000 W kg−1. These values represent a new performance record for supercapacitors based on biomass-derived carbons, indicating the great promise of these HPCs for high-performance electrochemical energy storage.