N, O self-doped hierarchical porous carbon materials for high-performance super-capacitors

Abstract

Biomass carbon materials have been widely used as electrode materials for super-capacitors (SC) due to their economic, environmental, and sustainable characteristics. In this work, we proposed that the Sapindus Mukorossi Peel (SMP) was used as a precursor to prepare a Sapindus Mukorossi Peel-based activated carbon material (SMPC) through carbonization and KOH activation. The morphology and structure of SMPC were characterized by various test methods. Cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS) were used to characterize its electrochemical performance. The results show that SMPC has suitable pore size distribution, a large number of heteroatom functional groups and excellent electrical conductivity. In addition, the amount of activator also has an important influence on the performance of SMPC. When the mass ratio of carbon material to KOH is 1:3, the prepared sample SMPC-3 has the largest specific surface area (SSA) was 1254.5 m2/g. Moreover, SMPC-3 also has excellent electrochemical properties, high specific capacitance (at 1 A/g, the specific capacitance can reach 314.5F/g), good cycle stability (at 5 A/g, cyclic charge and discharge 5000 times, the specific capacitance is only lost by 4.2%.), superior rate performance (when the current density is increased from 0.5 A/g to 10 A/g, the specific capacitance retention rate is 80.4%). Assembling SMPC-3 // SMPC-3 into a symmetrical SC shows higher energy density (at 0.1 A/g, the energy density is 6.68 Wh/Kg) and power density (at 5 A/g, the power density is 3250 W/Kg).