Three‐Dimensional Porous Carbon Materials from Coix lacryma‐jobi L. Shells for High‐Performance Supercapacitor

Abstract

AbstractThree‐dimensional (3D) porous carbon materials are widely concerned because of their excellent electrochemical performance in supercapacitors. Herein, a new porous Coix lacryma‐jobi L. shells‐based carbon (CSC) is prepared by carbonization and activation for super‐capacitors. The obtained CSC‐3 (CSC‐x, x: KOH/CSC mass ratio) possesses abundant porous structures, some functional groups with nitrogen and oxygen atoms, and good electrochemical performance. When the mass ratio of KOH to CSC is 3 : 1, the obtained CSC‐3 has the largest specific surface area (SSA, 1191.7 m2 g−1). Besides the material exhibits good electrochemical capability in the three‐electrode system with 6 m KOH aqueous electrolyte, such as desirable specific capacitance (at 0.5 A g−1, the specific capacitance is 413.5 F g−1), ideal rate performance (from 0.5 A g−1 to 10 A g−1, the specific capacitance retention rate is 70.86 %) and long cycle life (the specific capacitance only reduced by 2.47 % after 5000 cycles at 0.5 A g−1). Assembled symmetric supercapacitor (CSC‐3//CSC‐3) shows gratifying energy density (11.58 Wh Kg−1 at the power density of 324.93 W Kg−1 in 6 m KOH aqueous electrolyte and 14.67 Wh Kg−1 at 474.93 W Kg−1 in 1 m Na2SO4 aqueous electrolyte). This work provides possibility of utilizing waste Coix lacryma‐jobi L. shells to produce low‐cost and high‐performance super‐capacitor electrode materials for sustainable electrochemical energy storage.