Measuring the surface diffusivity of argon in nanoporous carbon.
Gas diffusion in porous media consists of surface hopping and non-surface ballistic/bulk diffusion. Unfortunately, only the overall diffusivity is usually measured, without being separated into various diffusion modes. Here, we report a numerical method to differentiate contributions from surface diffusion and non-surface diffusion for argon diffusion in nanoporous carbon using molecular dynamics simulations. The key is to truncate the argon trajectories based on the adsorption/desorption state, and thus attribute mass fluxes according to specific mechanisms during diffusion. Both the surface diffusivity and non-surface diffusivity increase and then decrease as a function of gas loading. Yet, surface diffusivity and non-surface diffusivity behave very differently as a function of the temperature and gas-substrate affinity of the nanoporous network.
Department of Material Science and Engineering, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, New York 12180, USA. shiy2@rpi.edu and Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, New York 12180, USA.
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Mi
Department of Material Science and Engineering, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, New York 12180, USA. shiy2@rpi.edu.
Yunfeng
http://orcid.org/0000-0003-1700-6049
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Shi