Modulating Water Slip Using Atomic-Scale Defects: Friction on Realistic Hexagonal Boron Nitride Surfaces

Atomic-scale
defects are ubiquitous in nanomaterials, yet their
role in modulating fluid flow is inadequately understood. Hexagonal
boron nitride (hBN) is an important two-dimensional material with
applications in desalination and osmotic power. Although pristine
hBN offers higher friction to the flow of water than graphene, we
show here that certain defects can enhance water slippage on hBN.
Using classical molecular dynamics simulations assisted by quantum-mechanical
density functional theory, we compute the friction coefficient of
water on hBN containing various vacancies (B, N, BN, B2N, and B3N) and the Stone–Wales defect. By investigating
two defect concentrations, we obtain friction coefficients ranging
from 0.4 to 2.6 times that of pristine hBN, leading to a maximum water
slip length of 18.1 nm on hBN with a N vacancy or a Stone–Wales
defect. Our work informs the use of defects to tune water flow and
reveals defective hBN as an alternative high-slip surface to graphene.