Enhanced Electrical Conductivity of Cellulose Nanofiber/Graphene Composite Paper with a Sandwich Structure

A novel conductive paper based on cellulose nanofiber (CNF) and reduced graphene oxide (RGO) with a sandwich structure was successfully prepared through step-by-step vacuum filtration followed by a chemical reduction process in which a CNF layer is sandwiched between two thin RGO layers. This unique design strategy not only provides a highly conductive network for its surface but also maintains the structural integrity of CNF. The sandwich-structured paper exhibits a significantly conductive anisotropy, and the in-plane electrical conductivity is drastically enhanced as 4382 S m(-1) with only 4 wt % RGO, whereas it is insulating along the cross-plane direction. This can be attributed to the RGO layers at the top and bottom surface connected in parallel. This high electrical conductivity is greatly superior to most of the cellulose/graphene composite papers obtained by conventional blending processes. Compared with the similar layer-by-layer assembly technique, the present method is more feasible and time saving. Moreover, the sandwich structured paper shows excellent mechanical strength and good flexibility, which may facilitate its applications in future flexible electronics.