The use of cellulose nanofibrils to enhance the mechanical properties of graphene nanoplatelets papers with high electrical conductivity

Mechanically flexible and high electrically conductive multilayered graphene nanoplatelets (GnP)/cellulose nanofibrils (CNF) composite papers were successfully fabricated through a vacuum-assisted self-assembly technique. The morphology observation showed that highly disassembled CNF were achieved by high-pressure homogenization of water-based cellulose slurry, and the homogenized CNF uniformly interpenetrated within the microporous GnP paper network. The analyses of mechanical properties and morphology suggest that the CNF effectively bridged the adjacent GnP sheets and efficiently strengthened the GnP papers by producing strong GnP/CNF interfacial interactions resulting from mechanical interlocking, van der Waals forces and hydrogen bonds between the GnP and the CNF. Moreover, it was noticed that hot-pressing pressure is necessary to be applied on samples to produce stronger papers with higher electrical conductivity. As the CNF loading reached 60 wt%, the Young's modulus and tensile strength of the hot-pressed GnP/CNF hybrid paper were significantly increased to 9.1 GPa and 57.7 MPa, respectively. In addition, a high electrical conductivity of 26.8 S/cm was retained for the paper with 30 wt% CNF. Our approach provides a facial and eco-friendly fabrication route to produce strong and highly conductive GnP/CNF papers which are of great practical appeal as a new type of nanomaterials in various fields.