Electrical conductivities and mechanical properties of porous cellulose nanofiber/reduced graphene oxide composites prepared with postreduction processes

Graphene-based conductive porous materials have been employed in various applications, such as sensors, energy devices, and magnetic shielding materials. Herein, we prepared porous cellulose nanofiber (CNF)/graphene composites with a two-step preparation strategy: fabrication of the porous CNF/graphene oxide (GO) precursors and postreduction of the GO to reduced GO (rGO). The porous precursors were prepared via freeze-drying to obtain honeycomb-like pore structures, and the GO was highly dispersed owing to its high affinity for CNFs. Thermal reduction of the CNF/GO precursor was performed at <150 degrees C for 48 h, resulting in a porous CNF/rGO composite with an electrical conductivity of 1.96 x 10(-4) S/m at 10 wt% GO owing to the electrically conductive paths in the rGO. Furthermore, the mechanical properties of the porous composites were characterized via compressive stress measurements. In addition, we demonstrated another postreduction method, i.e., chemical vapor reduction of CNF/GO with trimethylamine borane, which was completed within 30 min and provided a porous CNF/rGO composite with excellent conductivity (1.39 x 10(-3) S/m).