Effect of oxidation degree on the thermal properties of graphene oxide

Abstract

The introduction of graphene oxide into both metals and polymers has yielded materials with enhanced thermal properties. Of particular interest is functionalized graphene oxide containing substantially heterogeneously distributed functional groups. The thermal properties of graphene oxide were investigated using non-equilibrium molecular dynamics to understand mechanism of thermal transport at the nanoscale. The mechanism of phonon transport in the functionalized graphene sheet was discussed, and the structure factors limiting phonon transport were determined. The results indicated that the oxidation level influences the thermal conductivity greatly. There is a need to reduce the oxidation level in order to enhance phonon transport and reduce phonon scattering in the functionalized graphene sheet. Phonon transport in the functionalized graphene sheet at a high oxidation level is governed by the phonon mean free path associated with phonon-defect scattering. Oxygen-containing functional groups adversely influence the thermal properties due to enhanced phonon-scattering arising from the increased number of phonon-scattering centers. The intrinsic thermal conductivity of about 2480W/(mK) at room temperature agrees with existing data on single layer pristine graphene. At room temperature, the intrinsic thermal conductivity is around 72W/(mK) at an oxidation level of 0.35 and around 670W/(mK) at an oxidation level of 0.05. The phonon mean free path is limited mainly by interior defects and decreases with increasing the oxidation level due to enhanced phonon-defect scattering.