Unveiling the impact of atomic-scale defects and surface roughness on interfacial properties in hexagonal boron nitride

Abstract

Atomic-scale defects are ubiquitous in two-dimensional (2D) materials, yet their impact on interfacial properties remains insufficiently understood. Hexagonal boron nitride (hBN) is a 2D inorganic material with potential applications in nanofluidic devices and desalination. Here, we show that specific vacancy defects, in conjunction with monolayer roughness, can be used to manipulate the wetting and frictional behavior of hBN. Using combined first principles and classical modeling, we compute water contact angles and slip lengths on realistic hBN surfaces. Our findings demonstrate a significant alignment with experimental results. The combined effect of vacancy defects and surface roughness, known as exposed edges, provides a compelling explanation for the water contact angle (WCA) of 66° on pristine, uncontaminated hBN. Furthermore, this suggests that specific vacancy defects contribute to an enhanced hydrophilicity of hBN surfaces. The combined approach not only achieves high predictive accuracy but also predicts water slip length on hBN of roughly 1 nm, in agreement with the experiments. The findings emphasize the significance of incorporating vacancy defects and surface roughness in molecular simulations when modeling nanomaterial–water interfaces. This work will open up new avenues to understanding water flow through nanochannels and membranes, paving the way for revolutionary advancements in water purification and desalination.