Preparation of N,P Co-doped Porous Carbon Derived from Daylily for Supercapacitor Applications.

Biomass-derived activated carbon is a widely used electrode material for supercapacitors. One of the keys to preparing high-performance activated carbon is the selection of appropriate precursors. Daylily is a common edible herb and is widely planted in Asia. It is rich in nitrogen and phosphorus, so it can be used as a precursor of heteroatom-doped activated carbon. Herein, a daylily-derived porous carbon with a large specific surface area and high content of heteroatoms has been successfully prepared by a simple carbonization method. The as-prepared carbon materials showed a remarkable specific capacitance of 299.1 F/g at 0.5 A/g and excellent cycling stability of 99.6% after 4000 cycles at a current density of 1 A/g. Moreover, the assembled symmetric supercapacitor showed a high energy density of 21.6 Wh/kg at a power density of 598.2 W/kg in 6 M KOH electrolyte. These results demonstrate that the daylily-derived porous carbon is an excellent material for high-performance supercapacitors.