Hierarchical porous carbon materials synthesized from the castor oil/MgO solids for high-performance supercapacitors

A kind of biomass-based hierarchical porous carbons (HPCs) is easily synthesized by the direct pyrolysis of castor oil/MgO solids, in which the solids can be prepared by mixing appropriate amounts of MgO into castor oil. The morphology, microstructure, phase structure, textural property, surface element composition and thermal stability properties are studied for the achieved HPCs. It is demonstrated that the HPCs belong to a type of high-graphitization, graphene-like and foamed carbon materials with high specific surface area and wide pore size distribution. The HPC obtained at 900 °C (HPC-900) displays the highest specific surface area of 1013.17 m²g and more reasonable pore size distribution. Without the need of conductive agents, the HPC-900 exhibits a maximum capacitance (340 F g^-1at 0.5 A g^-1), excellent rate performance (70.1% of capacitance retention at high current density of 10 A g^-1) and a remarkable long-term cycling stability (about 99% capacitance retention after 9000 cycles) in the aqueous electrolyte of 6 M KOH. Meanwhile, assembled as-prepared sample into symmetrical supercapacitor, the HPC-900 provides a high energy and power density, with 8.6 Wh kg^-1and 426.7 W kg^-1in 1 M Na₂SO₄, respectively. The HPCs prepared based on castor oil show high potential for the electrode materials of supercapacitors.