Extended friction elucidates the breakdown of fast water transport in graphene oxide membranes

TL;DR

This study uses mesoscale simulations to reveal how oxygen functionalities and molecular friction in graphene oxide membranes significantly hinder fast water transport, contrasting with pristine graphene behavior.

Contribution

It introduces a mesoscale model incorporating spatially extended friction to explain water transport suppression in GO membranes, aligning with experimental observations.

Findings

Small oxygen functionalities drastically reduce GO permeability.

Inverted near-wall flow curvature indicates combined molecular and hydrodynamic effects.

The model offers a computationally efficient approach for nanomaterial water transport simulations.

Abstract

The understanding of water transport in graphene oxide (GO) membranes stands out as a major theoretical problem in graphene research. Notwithstanding the intense efforts devoted to the subject in the recent years, a consolidated picture of water transport in GO membranes is yet to emerge. By performing mesoscale simulations of water transport in ultrathin GO membranes, we show that even small amounts of oxygen functionalities can lead to a dramatic drop of the GO permeability, in line with experimental findings. The coexistence of bulk viscous dissipation and spatially extended molecular friction results in a major decrease of both slip and bulk flow, thereby suppressing the fast water transport regime observed in pristine graphene nanochannels. Inspection of the flow structure reveals an inverted curvature in the near-wall region, which connects smoothly with a parabolic profile in the bulk region. Such inverted curvature is a distinctive signature of the coexistence between single-particle Langevin friction and collective hydrodynamics. The present mesoscopic model with spatially extended friction may offer a computationally efficient tool for future simulations of water transport in nanomaterials.