Synthesis of biomass-derived N,O-codoped hierarchical porous carbon with large surface area for high-performance supercapacitor

Developing high-performance electrode by use of abundant natural materials as sustainable precursors is extremely important for promoting the practical application of supercapacitors. Herein, we present a promising strategy to convert biomass, sorghum seeds (SS), into efficient electrode material through pre-carbonization and combined KOH/melamine chemical activation. The derived electrode material possesses ultrahigh specific surface area (2132.1 m2 g−1), abundant hierarchical pores, and rich N, O doping, which are very beneficial for energy storage. Typically, the as-prepared carbon displays a high specific capacitance of 536.7 F g−1 at 0.5 A g−1 in 6 M KOH aqueous electrolyte in a three-electrode system. The assembled symmetric supercapacitors offer excellent cycling stability (97.6% retention after 15,000 cycles) and high specific energy (13.8 Wh kg−1 at specific power of 298.0 W kg−1). The study provides a facile, sustainable, and eco-friendly approach to produce hierarchical porous carbon from biomass for high-performance supercapacitors.