Molecular dynamics simulation of the effect of oxygen-containing functional groups on the thermal conductivity of reduced graphene oxide

Models of reduced graphene oxide (RGO) with different numbers of layers and simulation sizes were established and molecular dynamics simulations were performed to study the influence of oxygen-containing functional groups on the thermal conductivity (TC) of RGO. The results show that the TCs of both monolayer RGO (MRGO) and bilayer RGO (BRGO) increase with the increasing simulation length; under the same simulation size, the TC of BRGO is always lower than that of the MRGO. With the increasing content of functional groups, TCs of both MRGO and BRGO increase firstly and then decline. For MRGO, the optimum content occurs at about 2%. The phonon resonant frequency of MRGO with content of functional groups lower than 2% remains constant, and shifts to a lower frequency when the content of functional groups is higher than 2%; this confirms the effects of functional groups and wrinkling structure with ripples on the phonon scattering. For BRGO, the optimum content occurs at about 1%, which is lower than that for MRGO, since the interlayer distance of BRGO increases linearly with the increasing content of functional groups. Moreover, the changing trends of interaction energy and interlayer thermal resistance of BRGO are consistent with the TC change of BRGO.