Biomass-Derived Activated Porous Carbon from Rice Straw for a High-Energy Symmetric Supercapacitor in Aqueous and Non-aqueous Electrolytes

Abstract

Biomass-derived activated carbon materials were prepared by a two-step synthesis via carbonization followed by KOH activation of rice straw at 600 °C in an argon atmosphere. The formation of disordered micro- and mesopores on carbon by KOH chemical activation and the high specific surface area of ∼1007 m2 g–1 were confirmed by N2 adsorption–desorption. Further, the scanning electron microscopic analysis revealed the formation of disordered pores over the carbon surface, and the transmission electron microscopic analysis confirmed the formation and aggregation of ultrafine carbon nanoparticles of ∼5 nm in size after the carbonization and activation processes. The three-electrode cell in aqueous electrolyte shows high specific capacitance of 332 F g–1, with high specific capacitance retention of 99% after 5000 cycles. The fabricated symmetric supercapacitor device in aqueous 1 M H2SO4 electrolyte showed a high specific capacitance of 156 F g–1, with a high energy density of 7.8 Wh kg–1. The symmetric device...