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 m(2) g(−1) with optimized pore volume of 1.21 cm(3) g(−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 W h L(−1)) are achieved on the base of active material loading (~10 mg cm(2)) 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.