Nanoarchitectonics of graphene oxide with functionalized cellulose nanocrystals achieving simultaneous dual connections and defect repair through catalytic graphitization for high thermal conductivity

Graphene, with an extremely high intrinsic thermal conductivity of 5300 W/mK, is of special interest to meet thermal requirements in future wearable and high-power electronic devices. Generally, microscopic graphene sheets can be built into a macroscopic material by using graphene oxide (GO) as the precursor. However, both the defects on the basal plane of GO sheets and the lack of connections at their boundaries induce massive scattering of phonons and a low thermal conductivity. Herein, we solve the problem through the nano -architectonics of GO with nano Fe3O4 functionalized cellulose nanocrystals (Fe-CNC). During the assembly process, Fe-CNC were compounded with GO homogeneously and formed a composite GO/Fe-CNC film with an aligned lamellar structure. A subsequent thermal reduction at 1500 C resulted in the generation of Fe/Fe3C nanoparticles in the matrix of the reduced GO/Fe-CNC. During this process, the reduced GO (R-GO) sheets were dually connected by the Fe/Fe3C nanoparticles as well as the carbonized cellulose nanocrystals. Furthermore, the defects on the R-GO are repaired by Fe through a catalytic graphitization process. Thus, the scatterings of phonons at the adjacent sheet boundaries and on the basal plane of the R-GO sheets were reduced. A flexible and light weight composite film of reduced GO/Fe-CNC with a thermal conductivity of 1958.14 W/mK was obtained. The thermal conductivity is much higher than that of a pure R-GO film (388.72 W/mK) prepared under the same conditions. This assembly process achieved dual connections and defect repairs simultaneously and it provides an avenue for the design of graphene-based films with a high thermal conductivity.

Automated summary

In this study, graphene oxide (GO) was nano-architected with nano Fe3O4 functionalized cellulose nanocrystals (Fe-CNC) to enhance the thermal conductivity of GO/Fe-CNC composite films. Through a thermal reduction process at 1500°C, Fe/Fe3C nanoparticles were formed in the reduced GO/Fe-CNC matrix, which served as connections between the reduced GO (R-GO) sheets and carbonized cellulose nanocrystals. The defects on R-GO were repaired by Fe through a catalytic graphitization process, reducing the scatterings of phonons. The obtained flexible and lightweight composite film of R-GO/Fe-CNC exhibited a high thermal conductivity.