Microstructures and electrochemical characterization of graphene oxide/carboxymethylated cellulose nanofibril-derived hybrid carbon aerogels for freestanding supercapacitor electrodes

We herein report the morphological, thermal, electrical, and electrochemical properties of porous hybrid carbon aerogels prepared from carboxymethylated cellulose nanofibrils (c-CNF) and graphene oxide (GO, 1-10 wt %) via a facile process of freeze-drying, thermal stabilization, and carbonization at different temperatures of 800-1000 degrees C. During the carbonization, GO and c-CNF in the freeze-dried aerogel transformed into reduced GO (rGO) and porous carbon gel (CA), respectively. Morphological studies revealed that the porous hybrid carbon aerogels (rGO/CAs) had interconnected pores. The maximal electrical conductivity was achieved for the rGO/CA fabricated at the highest carbonization temperature of 1000 degrees C. With an increase in the amount of rGO, the electrical conductivity of the rGO/CAs increased to 0.91 S cm-1. For a three-electrode system in a PVA/H3PO4 gel electrolyte, the rGO/CA with 5 wt % rGO loading exhibited a high specific capacitance of 96.5 F g-1 at 0.5 A g-1. Also, the rGO/CA with 5 wt % rGO exhibited a rate capability of 10.3 % at 2 A g-1 and an energy density of 2.14 Wh kg-1 at a power density of 49.9 W kg-1. These results reveal that GO/c-CNF-derived hybrid carbon aerogels can be utilized as a potential material for the free-standing electrode of supercapacitors.