N/P Codoped Carbon Materials with an Ultrahigh Specific Surface Area and Hierarchical Porous Structure Derived from Durian Peel for High-Performance Supercapacitors

Activated N/P codoped carbon (A-NPC) materials with ultrahigh specific surface areas (SSA) and hierarchical porous structures were synthesized by a green and cheap method to enhance the electrochemical performance of electrical double-layer capacitors. Waste durian peel was used as a carbon precursor, (NH4)2HPO4 as N and P sources, and KOH as an activator. The obtained porous carbon material had an ultrahigh SSA (3416 m2 g–1), a hierarchical porous structure (84 vol % micropores), and appropriate N (2.17 at. %) and P (0.48 at. %) doping amounts. Synergy among these characteristics enabled the A-NPC to exhibit exciting specific capacitance (383.4 F g–1 at 0.5 A g–1), ideal rate performance (255.6 F g–1 at 20 A g–1), and fantastic cyclic performance (98.3% capacitance retention after 10 000 cycles at 5 A g–1) in the three-electrode device. This material could provide an energy density of 25.3 W h kg–1 when the power density was 400.5 W kg–1, to all-solid-state symmetrical capacitors and presented good cycle performance with a cycle retention rate of 97.6% at 2 A g–1 after 5000 cycles. A-NPC has potential applications in the supercapacitor field given its excellent properties.