Surface morphological effects on gas transport through nanochannels with atomically smooth walls

JH Qian and YH Li and HA Wu and FC Wang, CARBON, 180, 85-91 (2021).

DOI: 10.1016/j.carbon.2021.04.087

Gas transport through nanochannels is ubiquitous in nature and also plays an important role in industry. The gas flow in this regime can be described by the Knudsen theory, which assumes that molecules diffusely reflect on the confining walls. However, with the emergence of low dimensional carbon-based materials such as graphene and carbon nanotubes, it has been evidenced that this assumption might not hold for some atomically smooth surfaces, resulting in an anomalous enhancement of gas flux. In this study, we meticulously investigated the gas transport through nanochannels constructed by two selected kinds of 2D materials, graphene and molybdenum disulfide (MoS2), and interpreted the remarkable difference in gas flux through these two nanochannels. We revealed the underlying mechanism as the surface morphological effect on the gas collision with solid walls. Even a subtle distinction of surface roughness results in specular scattering on graphene surfaces while diffuse scattering on MoS2 surfaces. We also found that the curvature effect could reduce the surface roughness of interaction potential surfaces, leading to an additional enhancement on the gas flow rate. These insights are expected to deepen the understanding of gas transport in nanochannels, paving a promising way in the gas permeation control. (C) 2021 Elsevier Ltd. All rights reserved.

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