Equilibrium molecular dynamics were used to examine the self-diffusion and macroscopic diffusion of CH4/H2 mixtures adsorbed inside a (10,10) single-walled carbon nanotube. Equilibrium molecular dynamics could be used to determine the macroscopic diffusion coefficients of adsorbed mixtures by evaluating the matrix of Onsager transport coefficients. Earlier studies have indicated the diffusion of light gases adsorbed as single components in carbon nanotubes was extremely rapid compared to that in other known nanoporous materials. The results presented here indicate that extremely rapid diffusion could also occur for mixtures of adsorbed molecules. The rapid diffusion of adsorbed molecules and the strong coupling between the fluxes of the adsorbed species in a mixture have interesting implications for uses of carbon nanotubes in membrane-based applications.

Rapid Diffusion of CH4/H2 Mixtures in Single-Walled Carbon Nanotubes. Chen, H., Sholl, D.S.: Journal of the American Chemical Society, 2004, 126[25], 7778-9