Enhancing the electrochemical performance of biomass activated carbon through confining acid red 18 into the nanopores

The limitation of low energy density of carbon-based supercapacitors can be broken through introducing redox mediators into the electrolyte. Herein, biomass porous carbon CPPS-2 with a high specific surface area of 1649 m2/g was prepared by KOH activation. Capitalizing on the adsorption property of porous carbon, redox mediator, acid red 18 (AR18), was confined into the nanopores of CPPS-2 to fabricate the CPPS-2-18 electrode. After adsorbing 2.72 mg AR18, the specific capacitance of CPPS-2-18 is 568F/g at a current density of 1 A/g in 1 M H2SO4, which is as same as that of CPPS-2 in 1 M H2SO4 + 10 mM AR18, however, the rate performance and coulombic efficiency of CPPS-2-18 are higher than those of CPPS-2. The results reveal that the redox reaction in nanopores of CPPS-2-18 is more reversible than that on the surface of CPPS-2. Meanwhile, the symmetric supercapacitor based on CPPS-2-18 achieves a maximum energy density of 23Wh/kg and power density of 6000 W/kg. Besides, the self-discharging behavior of CPPS-2 is restrained by confining AR18 into the nanopores.