Nanocellulose-derived highly porous carbon aerogels for supercapacitors

High-surface-area carbon aerogels are synthesized by pyrolysis of nanocellulose aerogels that are prepared by dissolving of cellulose microcrystalline in NaOH aqueous solutions followed by gelation, regeneration and freeze drying or supercritical CO2 drying. The obtained carbon aerogels are further treated via a CO2 activation process. The result shows that the nanocellulose aerogels dried by supercritical CO2 exhibit a high specific surface area (299 m2/g) and the obtained carbon aerogels preserve the interconnected 3D nanostructure and have a high specific surface area of 892 m2/g and a high pore volume of 1.80 cm3/g, which increase to 1873 m2/g and 2.65 cm3/g respectively after CO2 activation. The highly porous and interconnected nanostructure provides efficient migration of electrolyte ions and electrons, which makes the resultant activated carbon aerogels exhibit excellent electrochemical performance for supercapacitors. The specific capacitances reach 302 and 205 F/g at a current density of 0.5 and 20 A/g respectively within a potential window of −1.0 to 0 V in 6 M KOH solution. The capacitance retains 92% after 4000 cycles of charge/discharge, implying a good cycling stability.