Diffusion of gas molecules on multilayer graphene surfaces: Dependence on the number of graphene layers

The diffusion of gas molecules on multilayer graphene surfaces is of great importance for a wide range of applications in gas-related industries. This study calculates diffusion coefficients for gas diffusion on single layer or multilayer graphene surfaces based on molecular dynamics simulations with a major emphasis on the effect of the number of graphene layers. The results show that the gas diffusion on these graphene surfaces is mainly controlled by molecular collisions in the adsorption layer; because the contributions of the gas adsorption energy and the gas collision energy are always comparable with the gas adsorption energy becoming slightly stronger with increasing number of graphene layers. Therefore, the surface diffusion coefficient decreases gradually with increasing number of graphene layers owing to the larger number of adsorbed molecules on graphene surfaces with more layers. Notably, the diffusion coefficients do not depend strongly on the number of graphene layers when there are a large number of graphene layers due to the limited interaction distance between the gas molecules and the graphene atoms. Furthermore, the variations of the surface diffusion coefficient with the number of graphene layers and the gas species are confirmed from the probability distributions of the molecular jump length on the graphene surface in a given time period.