Functional porous carbon derived from waste eucalyptus bark for toluene adsorption and aqueous symmetric supercapacitors

It is of great significance to synthesize functional porous carbon from renewable waste biomass resources to solve the problems of energy storage and environmental pollution. Herein, the eucalyptus bark was converted into porous carbon materials for toluene adsorption and aqueous symmetric supercapacitors by hydrothermal treatment combined with KOH activation. Toluene adsorption experiments indicated that the toluene adsorption capacities of BPCs increased with increase of activated temperature and activator concentration, and the toluene adsorption capacities of BPCs were inversely related to adsorption temperature and relative humidity. The effects of structural characteristics and functional groups on toluene adsorption were analyzed in detail. Besides, the supercapacitance performance of samples under different preparation conditions was tested, the BPC-3-600 electrode exhibited the best specific capacitance of 263.2 F g−1 at 0.5 A g−1 and 207.5 F g−1 at 10 A g−1 in a three-electrode system using 6 M KOH as the electrolyte. Moreover, the aqueous symmetric supercapacitor assembled in 6 M KOH showed a high specific capacitance of 191.2 F g−1 at 0.2 A g−1 and an outstanding capacitance retention of 105.1 % at 5 A g−1 after 10,000 cycles. Most importantly, the supercapacitor assembled in 1 M Na2SO4 can provide an energy density as high as 10.5 Wh kg−1 at a power density of 159.5 W kg−1, and a remarkable energy density of 5.2 Wh kg−1 can be retained even at a power density as high as 12,480.0 W kg−1.