Enhanced Graphene-Water Thermal Transport via Edge Functionalization without Compromising In-Plane Thermal Conductivity

TL;DR

This study demonstrates that selective edge functionalization of graphene nanoribbons with hydroxyl groups significantly enhances interfacial thermal conductance with water while largely preserving in-plane thermal conductivity, offering a promising strategy for thermal management.

Contribution

It introduces a novel approach of edge-specific functionalization to improve graphene-water thermal transport without degrading in-plane phonon conduction.

Findings

Edge functionalization increases interfacial conductance by over eight times.

In-plane thermal conductivity is largely preserved with edge functionalization.

Non-monotonic relationship between edge functionalization ratio and in-plane conductivity.

Abstract

Interfacial thermal transport between graphene and water plays a critical role in a wide range of thermal and energy applications. Although chemical functionalization can significantly enhance graphene-water interfacial thermal conductance, it often degrades graphene's intrinsic in-plane phonon transport. In this work, we perform a systematic deep neural network molecular dynamics study comparing edge-functionalized graphene nanoribbons with surface-functionalized graphene in aqueous environments. We demonstrate that functionalizing only 10% of the ribbon edges with hydroxyl groups increases the graphene-water interfacial thermal conductance by more than eightfold, primarily due to strengthened interfacial interactions and improved wettability at the edges. In contrast to basal-plane oxidation, edge functionalization largely preserves in-plane thermal conductivity. Importantly, hydroxyl edge groups exert competing effects on phonon transport: they introduce additional boundary scattering that suppresses heat conduction, while simultaneously passivating dangling bonds at bare edges, thereby reducing phonon localization and edge-induced scattering. This competition leads to a non-monotonic dependence of in-plane thermal conductivity on edge functionalization ratio. These results establish edge functionalization as an effective strategy for enhancing graphene-water interfacial thermal transport without sacrificing intrinsic phonon transport properties.