Hydrothermal, KOH-assisted synthesis of lignin-derived porous carbon for supercapacitors: value-added of lignin and constructing texture properties/specific capacitance relationships

Searching for good-natured feedstocks and understanding the texture property of porous carbon/specific capacitance relationships have long been highly desirable. Herein, hydrothermal and KOH were used to assist the synthesis of lignin-derived porous carbons (LPCs) with high specific surface area for supercapacitors. The as-synthesized LPC-150 and LPC-200 had a specific surface area of 3033.88 m2/g and 3178.36 m2/g, respectively, with a specific capacitance of 214.03 F/g and 201.69 F/g at 0.50 A/g. In the range from 2448 m2/g to 3178 m2/g, increasing the specific surface area again possesses no remarkable effect on the specific capacitance. Meanwhile, the specific surface area and the pore-wall thickness together determine the specific capacitance. When using a three-electrode configuration with a 6 mol/L KOH electrolyte, the volumetric surface area rather than the ultrahigh specific surface area can be employed as a general predictor of specific capacitance in the low current density ranging from 0.50 to 10.00 A/g.