Tangerine peel-derived nitrogen doped porous carbon as electrode material for high-performance supercapacitors

Nitrogen-doped hierarchical meso/microporous carbons were successfully synthesized from tangerine peel through pyrolytic activation at elevated temperature in nitrogen atmosphere, utilizing potassium hydroxide as activator and melamine as nitrogen source. The resulting optimal hierarchical carbon (denoted as NBC-600) possessed a high specific surface area of 601.49 m²·g⁻¹, along with a nitrogen doping level of 2.5 %, both of which contribute significantly to its outstanding supercapacitive performance. Electrochemical evaluations reveal that the NBC-600 electrode delivers an excellent gravimetric specific capacitance of 304.4 F·g⁻¹, accompanied by excellent cycling stability and rate capability. Moreover, a symmetric two-electrode supercapacitor assembled with NBC-600 achieves an energy density of 26.8 Wh·kg⁻¹ at a corresponding power density of 250.0 W·kg⁻¹. Notably, the device demonstrates exceptional cycling stability, retaining 96.9 % of its initial capacitance after 10,000 charge-discharge cycles at a current density of 10 A·g⁻¹. The superior electrochemical properties of NBC-600 surpass that of numerous biomass-derived hierarchical porous carbons, underscoring its feasibility as a cost efficient and high-performance electrode material for next-generation supercapacitors.