Lignosulfonate-modified corncob cellulose biochar as an electrode material for high-performance supercapacitor application

Because of its wide range of material sources, high specific surface area, and advantageous electrochemical characteristics, cellulose biochar derived from natural lignocellulosic raw materials has been extensively applied as electrodes for energy storage materials. To produce carbon materials with improved qualities, lignocellulosic substrates often need to be pretreated, activated, and modified. In this study, corncob was processed with bisulfite to break down its recalcitrant structure, followed by direct use of the pretreated substrate to avoid the post-pretreatment washing step and take full advantage of the generated lignosulfonate (LS) in the next pyrolysis process. The residual LS in the pretreated sample not only increased the specific surface area of the corncob-biochar, but also introduced the heteroatom S. The biochar obtained through pyrolysis at 900 °C with KOH activation from unwashed pretreated corncob (ABU-900) had a specific surface area of 3130 m 2 /g, and it displayed a high coulombic efficiency of 94.1% after 5000 cycles in a three-electrode system. Owing to the successful introduction of heteroatoms, an asymmetric supercapacitor device (ABU-900//activated carbon) delivered an excellent specific capacitance of 141.2 F/g at a current density of 1 A/g and an energy density of 43.7 Wh/kg with a power density of 619 W/kg. This work offers a new and simple route for preparing cellulose biochar-based electrodes from lignocellulose waste.