Abstract
How to address the destruction of the porous structure caused by elemental doping in biochar derived from biomass is still challenging. In this work, the in-situ nitrogen-doped porous carbons (ABPCs) were synthesized for supercapacitor electrode applications through pre-carbonization and activation processes using nitrogen-rich pigskin and broccoli. Detailed characterization of ABPCs revealed that the best simple ABPC-4 exhibited a super high specific surface area (3030.2-3147.0 m(2) g(-1)) and plentiful nitrogen (1.35-2.38 wt%) and oxygen content (10.08-15.35 wt%), which provided more active sites and improved the conductivity and electrochemical activity of the material. Remarkably, ABPC-4 showed an outstanding specific capacitance of 473.03 F g(-1) at 1 A g(-1). After 10,000 cycles, its capacitance retention decreased by only 4.92% at a current density of 10 A g(-1) in 6 M KOH. The assembled symmetric supercapacitor ABPC-4//ABPC-4 achieved a power density of 161.85 W kg(-1) at the maximum energy density of 17.51 Wh kg(-1) and maintained an energy density of 6.71 Wh kg(-1) when the power density increased to 3221.13 W kg(-1). This study provides a mixed doping approach to achieve multi-element doping, offering a promising way to apply supercapacitors using mixed biomass.