Microwave-assisted synthesis of Cu-doped hierarchical porous carbon aerogels derived from lignin for high-performance supercapacitors

Abstract

Hierarchical porous carbon aerogels with a high specific surface area and excellent electrochemical performance were synthesized by pyrolysis and CO2 activation of Cu-doped lignin-based aerogels. The Cu-doped lignin-based aerogels were prepared by a microwave assisted sol-gel process of alkali lignin, resorcinol, and formaldehyde under the catalysis of CuCl2 · 6H2O. The microwave assisted sol-gel process reduces the gelation time from weeks to 10 min. The Cu-doped lignin-based carbon aerogels exhibit an interconnected porous network structure, a high specific surface area of 431 m2 g−1, a large total pore volume of 0.24 cm3 g−1, and a high specific capacitance of 222.96 F g−1, which increase to 899 m2 g−1, 0.63 cm3 g−1 and 257.65 F g−1 after CO2 activation process, respectively. The microporosity of Cu-doped lignin-based carbon aerogels reached 66.7%, which decreased to 47.6% after CO2 activation process. The activation process contributes to the fusion of adjacent micropores into larger ones. In addition, the CO2 activated Cu-doped lignin-based carbon aerogels exhibit outstanding cycling stability. The specific capacitance retains 95% after 2000 cycles at the current density of 20 A g−1. These findings open up the rapid fabrication of low-cost and high-performance carbon aerogels and show potential application in energy storage.