Friction of Water on Graphene and Hexagonal Boron Nitride from ab initio Methods: Very Different Slippage Despite Very Similar Interface Structures

TL;DR

This study uses ab initio molecular dynamics to compare water friction on graphene and boron nitride, revealing significant differences in friction despite similar interface structures, due to electronic structure effects.

Contribution

First application of ab initio MD to connect nanoscale water structure with friction on graphene and boron nitride surfaces.

Findings

Friction coefficient on boron nitride is about three times larger than on graphene.

Similar interface structures but different energy landscape corrugation.

Electronic structure effects influence nanoscale water transport.

Abstract

Friction is one of the main sources of dissipation at liquid water/solid interfaces. Despite recent progress, a detailed understanding of water/solid friction in connection with the structure and energetics of the solid surface is lacking. Here we show for the first time that \textit{ab initio} molecular dynamics can be used to unravel the connection between the structure of nanoscale water and friction for liquid water in contact with graphene and with hexagonal boron nitride. We find that whilst the interface presents a very similar structure between the two sheets, the friction coefficient on boron nitride is $\approx 3$ times larger than that on graphene. This comes about because of the greater corrugation of the energy landscape on boron nitride arising from specific electronic structure effects. We discuss how a subtle dependence of the friction on the atomistic details of a surface, that is not related to its wetting properties, may have a significant impact on the transport of water at the nanoscale, with implications for the development of membranes for desalination and for osmotic power harvesting.