Molten salt synthesis of nitrogen-doped hierarchical porous carbon from plantain peels for high-performance supercapacitor

• A green and scalable molten salt method is employed to synthesize hierarchical porous carbon from plantain peels. • A high SSA of 959 m 2 /g, interconnected pore structure and highly defective and graphitized framework obtained. • The N -doped porous carbon exhibited high specific capacitance of 550 F/g at a current density of 1 A/g in a three-electrode setup. • Capacitance retention of 99% after 1000 cycles at 4 A/g This work employs a non-corrosive and non-toxic molten salt combination of NaCl and KCl as an activation agent in an air environment to synthesize nitrogen-doped hierarchical porous carbon from plantain peels at 800 °C for supercapacitor application. Due to the synergistic effect of nitrogen doping, the synthesized nitrogen-doped activated unripe porous carbon (AUPN) has a hierarchical (micro-meso-macropores) porous structure and a high surface area of 959 m 2 /g, providing sufficient active sites for charge storage, rapid electrolyte and ionic mobility. X-ray diffraction and Raman spectroscopy analysis revealed the formation of a carbon product with a limited degree of graphitization and the crystallite size (L a ), which is valuable for evaluating the defects caused by nitrogen doping. In a three-electrode cell with a 6 M KOH electrolyte, AUPN recorded a specific capacitance of 550 F/g at 1 A/g. After 1000 cycles, capacitance retention was 99% at 4 A/g. Compared to other reported porous carbon materials, the overall electrochemical performance of AUPN is superior. This is due to the abundant nitrogen-doping, which introduces pseudocapacitance and increases the surface wettability of the porous carbon, resulting in a decrease in ionic-transport resistance. These findings indicate that this green and scalable technique is a potential synthesis method for producing porous carbon materials for energy storage applications.