Porous Carbon Nanosheets with Abundant Oxygen Functionalities Derived from Phoenix Seeds for High‐Performance Supercapacitor

Biomass‐derived porous carbon with abundant electro‐active oxygen functionalities was prepared by controlled pyrolysis and KOH activation of phoenix seeds, in which KOH not only acts as activation reagent constructing porous structure, but also serves as adjustor tuning the C/O ratio of the final carbon products. The obtained porous activated carbon nanosheet (PACN) possesses nanosheet morphology with nanoporous structure, large surface area (1166 m 2 /g) and high oxygen content of 10.2 at. %. As electrode for supercapacitor in 2.0 M H 2 SO 4 electrolyte, the PACN achieves a high capacitance of 376 F/g at current density of 0.5 A/g, good rate capability (230 F/g at 20.0 A/g) and an excellent cycling stability with 99% capacitance retention over 10000 cycles, which can be attributed to the large surface area and rich electro‐active oxygenic functionalities. The symmetric supercapacitor with PACN exhibits a superior energy density of 5.9 Wh/kg at 3.5 kW/kg. The present work highlights the controlled pyrolysis and KOH activation strategy as a facile approach to utilize a potential biomass resource for low‐cost and high‐performance electrochemical capacitors.