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.