Sodium lignosulfonate-derived hierarchical porous carbon electrode materials for supercapacitor applications

In order to improve the low specific capacity and low rate performance of supercapacitors, it is essential to effectively modulate the microscopic defects and pore structures in the porous carbon materials that are the main energy storage sites. Herein, two biomass derivatives, sodium lignosulphonate and sodium humate were used to prepare high porosity hierarchical porous carbon materials doped with N, O and S atoms, with boric acid as template and activation by KOH. The hierarchical porous carbon has a high specific surface area of 1588.4 m2·g−1 and a high pore volume of 1.4 cm3·g−1. As an electrode material for a supercapacitor, the specific capacitance was as high as 318.3 F·g−1 at a current density of 0.5 A·g−1 in a three-electrode system with a 6 M KOH electrolyte, and had excellent rate performance with 72.8 % retention even at high current densities of 10 A·g−1. The symmetric supercapacitor possesses an energy density of 17.7 Wh·kg−1 at 59.8 W·kg−1 and exhibits excellent cycle stability with a retention rate of 97.2 % after 10,000 cycles. This work proposes an effective method for converting biomass derivatives into high-performance supercapacitor electrode materials.