Biomass waste derived functionalized hierarchical porous carbon with high gravimetric and volumetric capacitances for supercapacitors

Abstract

Abstract Preparation of porous carbon from biomass materials shows great potential in the field of supercapacitor. Porous carbon obtained by KOH activation (up to 2000 m2 g−1) shows excellent gravimetric capacitance up to 300 F g−1. Nevertheless, the volumetric performances of these porous carbons are rather poor (60–130 Fcm−3) owing to the high porosity and low density. Herein, we develop a facile method to prepare nitrogen and sulfur co-doped hierarchical porous carbon (NSPC) derived from foxtail grass seeds using NaHCO3/KHCO3 as activation agent. Benefiting from the suitable specific surface area (819 m2 g−1), interconnected porous structure and rich heteroatoms, the as-prepared NSPC-600 displays high gravimetric capacitance (358.0 F g−1) and volumetric capacitance (243.4 F cm−1) at 0.5 A g−1 and impressive cycling durability. Besides, the as-fabricated symmetric supercapacitor (SSC) displays an energy density of 18.2 Wh L−1, which is higher than the reported porous carbon-based SSCs. These excellent characteristics provide a facile, eco-friendly strategy to prepare porous carbon with high gravimetric and volumetric capacitances for supercapacitors.