Green synthesis of hierarchical nitrogen-doped porous activated carbon material based on biomass waste for high-performance energy storage as supercapacitor

Superior electrochemical capacitance properties can be achieved with biomass-based carbon materials synthesized with appropriate activation methods. In this study, chestnut shells were employed as a biomass-derived carbon precursor for the development of high-performance electrode materials for electrochemical energy storage applications. The chestnut shells were first pyrolyzed through chemical activation with sodium hydroxide to produce N-doped NaOH-CS. Then, the surface properties were further improved by nitrogen (N) atom doping to the AC sample using ammonia. Due to the favorable pore structure, specific surface area, and N content, the N-doped NaOH-CS supercapacitor material exhibits excellent capacitive performance of 625 F/g at 1 A/g, representing a 500 % increase compared to the NaOH-CS material. Different analytical methods are used for the characterisation of the materials. Experimental results confirm that the N-doped NaOH-CS supercapacitor material shows a stability of 84.6 % over 5000 consecutive cycles. At a current density of 1 A/g, the NaOH-CS-GCE//AC material delivers an energy density of 21.2 Wh/kg with a power density of 558 W/kg. When the current density increases to 8 A/g, it maintains a comparable energy density of 22.0 Wh/kg while achieving a significantly higher power density of 4400 W/kg. These findings demonstrate the suitability of biomass waste obtained from chestnut shells for high-performance electrode materials.