Role of surface oxidation in enhancing heat transfer across graphene–water interface via Thermal Boundary Resistance modulation

Functionalization or surface oxidation is a fundamental requirement for carbon-based nanoparticles to prevent self-aggregation and thus be homogeneously dispersed in a fluid. However, the presence of functional or oxidation groups dramatically affects the thermal boundary resistance (TBR) and thus the overall thermal properties of the resulting colloidal suspension. In this work, we systematically investigate through molecular dynamics simulations the effect of oxidation degree on the TBR at the graphene-water interface. We find a linear correlation between the oxidation degree and the thermal boundary conductance (reciprocal of TBR) at low-to-moderate degrees, which can be interpreted through a parallel thermal resistance model, considering the contributions of pristine graphene and hydroxyl (-OH) groups, confirming our previous experimental findings. Results are interpreted in the light of wettability, roughness and phonon density of states, which highlight the higher affinity between water and graphene as the oxidation degree rises. More generally, beyond the specific case study discussed in this work, this systematic approach can be applied to other solid-liquid interfaces to further explore the general correlation between TBR and surface oxidation degree.