From rice bran to high energy density supercapacitors: A new route to control porous structure of 3D carbon

Controlled micro/mesopores interconnected structures of three-dimensional (3D) carbon with high specific surface areas (SSA) are successfully prepared by carbonization and activation of biomass (raw rice brans) through KOH. The highest SSA of 2475 m² g^-1 with optimized pore volume of 1.21 cm 3g^-1 (40% for mesopores) is achieved for KOH/RBC = 4 mass ratio, than others. The as-prepared 3D porous carbon-based electrode materials for supercapacitors exhibit high specific capacitance specifically at large current densities of 10 A g^-1 and 100 A g^-1 i.e., 265 F g^-1 and 182 F g^-1 in 6 M KOH electrolyte, respectively. Moreover, a high power density ca. 1223 W kg^-1 (550 W L^-1) and energy density 70 W h kg^-1 (32 Wh L^-1) are achieved on the base of active material loading (∼10 mg cm²) in the ionic liquid. The findings can open a new avenue to use abundant agricultural by-products as ideal materials with promising applications in high-performance energy-storage devices.