Liquid nitrogen-controlled direct pyrolysis/KOH activation mediated micro-mesoporous carbon synthesis from castor shell for enhanced performance of supercapacitor electrode

Abstract

Direct pyrolysis/KOH activation of carbon from castor shell biomass is an economical combination of two processes to breakdown biomass lignin effectively. The advanced liquid nitrogen-controlled direct pyrolysis/KOH activation technique is even a shortened process, which optimizes the fugacious bond reformation for enhancing supercapacitors’ performance. Novel quenching of the red-hot activated carbon (heated at 800 °C) in liquid nitrogen is peculiar to the demonstrated structural changes. The desired throughput designated nKAC exhibited a high specific surface area of 1468 m2 g−1 over the initial 1131 m2 g−1 for KAC. In 6 M KOH electrolyte, the nKAC electrode exhibited a high specific capacitance of 481 F g−1 at 1 A g−1 and an excellent rate capability of 298 F g−1 at 30 A g−1. In symmetric two electrodes test, the electrodes of nKAC show a high energy density of 17.75 Wh kg−1 at 0.5 A g−1 in 1 M Na2SO4 electrolyte compared with 14.75 Wh kg−1 of KAC electrodes. Furthermore, the nKAC still maintained a high energy density of 12.4 Wh kg−1 at 5.0 A g−1 corresponding to a high power density of 4500 W kg−1. This simple and green method has potential applications in the synthesis of porous carbon based on waste biomass for enhancing performance of electrode materials.