Influence of Nitrogen Doping and Pre‐Carbonization on the Performance of Lignin‐Derived Activated Carbon for Supercapacitor Applications

Abstract Nanostructured carbons are widely used as active materials for supercapacitor applications owing to their high specific surface area and electrical conductivity. Biomass waste‐derived materials can be sustainably produced. In this work, highly porous activated carbon was prepared from lignin waste for supercapacitor applications, and the effects of nitrogen doping and a pre‐carbonization treatment on the final performance were investigated. Particularly, activated carbonized lignin (ACL) and activated lignin (AL) samples were prepared with or without a pre‐carbonization step, respectively, and with or without nitrogen doping. Nitrogen doping of the samples was found to decrease the capacitance owing to the loss of critical oxygen‐containing functional groups, which provide pseudocapacitance. Meanwhile, the use of a pre‐carbonization treatment greatly improved the surface area and capacitance of the materials. Sorptometry analysis indicated that ACL and AL have high specific surface areas of 3174 and 2289 m 2 g −1 , respectively. ACL achieved a specific capacitance of 306.4 F g −1 and 292.1 F g −1 in 1 mol L −1 KOH and H 2 SO 4 , respectively. Furthermore, the contribution of a pre‐carbonization treatment to improve the surface area and maintain the presence of oxygen‐containing functional groups was identified as beneficial towards improving the pseudocapacitance properties of the porous carbon materials.