N-doped porous carbon derived from pomelo peel for high-performance supercapacitor

N-doped pomelo peel-derived porous carbon (N-ppPC) is prepared by a combined hydrogel dispersion-activation and freeze-drying process. The obtained layered N-ppPC exhibits excellent capacitive behavior due to its suitable pore-structure and heteroatom doping level, thin layer-thickness as well as high specific surface area. It delivers a high specific capacitance (438 F g −1 at 0.5 A g −1 ) in a three-electrode system. For an assembled coin-type symmetric supercapacitor in aqueous electrolyte, the specific capacitance reaches 264 F g −1 (0.5 A g −1 ), and after 10,000 cycles at a current density of 2 A g −1 , the capacitance retention is as high as 90.9 %. While in ionic liquid electrolyte, the specific capacitance reaches 140 F g −1 (0.2 A g −1 ) with a capacitance retention of 62.9 % at a high current density of 10 A g −1 . Especially, it achieves a high energy density of 59.5 Wh kg −1 at a power density of 174.9 W kg −1 .