Self-template synthesis of nitrogen-doped porous carbon derived from rice husks for the fabrication of high volumetric performance supercapacitors

Porous carbons (PCs) derived from biomass have been successfully used in the fabrication of supercapacitors as electrode material. Their large surface area and developed porosity significantly contribute to the high gravimetric capacitance, but deteriorate the carbon density leading to low volumetric capacitance. PCs with high volumetric capacitance are more desirable for portable energy storage devices. Herein, high volumetric performance nitrogen-doped PCs were prepared by the pyrolysis of urea-impregnated rice husks. The self-template effect of rice husks created hierarchical porosity for ion storage and transport. The decomposed urea introduced nitrogen-containing groups to generate pesudocapacitance without sacrificing carbon density. As a result, the resultant product 4NPC-800 exhibited high volumetric capacitance of 306 F cm(-3) at 0.5 A g(-1) in 1 M H2SO4 electrolyte. The assembled symmetric supercapacitor presented a superior volumetric energy density of 15.24 W h L-1 at 594 W L-1 and outstanding cycling stability. The favorable capacitive behavior of 4NPC-800 demonstrated its potential as carbon-based electrode applied in high performance supercapacitors.