Thermal characteristics of graphene nanoribbons endorsed by surface functionalization

In this paper, the thermal characteristics of graphene nanoribbons with surface hydrogenation are investigated using Reverse Non-Equilibrium Molecular Dynamics (RNEMD) simulations. Thermal conductivity of graphene nanoribbons with fully hydrogenated domain (graphane) are studied by calculating the Kapitza conductance across the graphene-graphane interface. Thermal conductivity of hybrid nanoribbon is revealed to depend on the length as well as charity and initial temperature, and been systematically interpreted from the perspectives of morphology and phonon vibrational spectra. More interestingly, remarkable thermal rectification is noticed for hybrid nanoribbon with graphene-graphane interface. The thermal conductivity under heat flux from graphane to graphene is higher than that under opposite heat flux. Such thermal rectification decays with the length of nanoribbon and a critical length of 10 nm is identified for single layer nanoribbon beyond which the thermal rectification disappeared. We also studied the thermal properties of graphene nanoribbon with gradient hydrogen arrangement at the surface. Gradient hydrogenation can provide graphene nanoribbon with similar thermal rectification while eliminating the dependency on chirality and length. The proposed gradient hydrogenation can be used for length-insensitive thermal diode with practical application. Our work reveals detailed thermal characteristics of hydrogenated graphene nanoribbons, and provides a possible design of carbon-based thermal diodes.