Preparing hierarchical porous carbon aerogels based on enzymatic hydrolysis lignin through ambient drying for supercapacitor electrodes

Hierarchical porous lignin-based carbon aerogels, synthesized through a low-cost and simple method, are promising for applications in supercapacitor electrodes. Lignin-based carbon aerogels are prepared by pyrolysis and KOH activation of lignin-based aerogels. Lignin-based aerogels are prepared by mixing of enzymatic hydrolysis lignin (L), resorcinol (R) and formaldehyde (F) under the catalysis of Na2CO3 (C) followed by gelation, aging and ambient drying process. The results show that lignin-based carbon aerogels with a L/(L + R) ratio of 20%, exhibit a high specific surface area of 779 m(2)/g, a large total pore volume of 0.48 cm(3)/g, and a large micropore volume of 0.29 cm(3)/g. The obtained lignin-based carbon aerogels exhibit an interconnected, hierarchical porous network structure and a high degree of graphitization, which further contributes to their excellent electrochemical performance as electrodes in supercapacitors. The specific capacitance reaches 142.8 F/g at a current density of 0.5 A/g. Even at a large current density of 10 A/g, the specific capacitance of the CA-L20 electrode remains 112.5 F/g. After 2000 charge/discharge cycles, the specific capacitance still maintains 96% of its initial value, which indicates an excellent durability.