Ultratough cellular films from graphene oxide hydrogel: A way to exploit rigidity and flexibility of two-dimensional honeycomb carbon

Abstract

The mechanical properties of hierarchically porous graphene films are unsatisfactory for the wide applications requiring toughness. Here, we report an innovative approach to construct anisotropic graphene-based cellular films with an oriented and interlinked microstructure, which can provide both high strength (2.4 ± 0.2 MPa) and extraordinary toughness (0.10 ± 0.01 MJ m−3). The specific strength (30 ± 2 MPa/(Mg m−3)) and specific modulus (8.4 ± 0.4 × 102 MPa/(Mg m−3)) of the porous films are even comparable to tough cancellous bone. The graphene oxide hydrogel films obtained from the shear and relaxation procedure are then reduced with hydroiodic acid/acetic acid, which solidifies the oriented and interlinked structures to give the final porous films. By this approach, the intrinsic features of an individual graphene sheet, such as high in-plane rigidity and excellent out-of-plane flexibility, are fully exploited. The great enhancement of strength and toughness is proved to be realized by a synergistic cooperation mechanism, where the unique architecture bears stress through tensile strain of oriented graphene sheets and dissipates energy through bending deformation of the bridged graphene sheets. The proof-of-concept design and deep understanding of the structure-property relationship will be of benefit to the fabrication and applications of graphene-based devices.