One step synthesis of N, P co-doped hierarchical porous carbon nanosheets derived from pomelo peel for high performance supercapacitors.

Ammonium dihydrogen phosphate (NH4H2PO4) was used as an activator and co-dopant to induce the synthesis of N, P co-doped porous carbon nanosheets (NPCNs) from pomelo peel for using as high-performance supercapacitors. Pomelo peel has a unique sponge-like structure in which NH4H2PO4 particles can be evenly embedded. The pore structure and heteroatomic doping amount of NPCNs were controlled by adjusting the pyrolysis temperature. As a result, the optimal sample exhibits high specific capacitance (314 ± 2.6 F g-1) and rate capability (82% of capacitance retention at 20 A g-1). NPCNs-750 was further employed in a symmetrical supercapacitor (NPCNs-750//NPCNs-750 SSC) with 2 M Li2SO4 electrolyte, and exhibits a high energy density of 36 ± 1.5 W h kg-1 at a power density of 1000 W kg-1, with excellent cycling stability with 99% retention after 10,000 cycles. A series of excellent results show that this pollution-free and cost-effective method can be used for the design and preparation of high-performance supercapacitor electrode materials.