Measuring the surface diffusivity of argon in nanoporous carbon

Area of Science:

• Materials Science
• Physical Chemistry
• Computational Science

Background:

• Gas diffusion in porous media involves complex mechanisms like surface hopping and bulk diffusion.
• Current methods often measure only overall diffusivity, lacking separation of individual diffusion modes.

Purpose of the Study:

• To develop and present a novel numerical method for differentiating surface and non-surface diffusion contributions.
• To analyze argon diffusion in nanoporous carbon, separating its distinct diffusion pathways.

Main Methods:

• Utilized molecular dynamics simulations to model gas diffusion.
• Developed a trajectory truncation technique based on adsorption/desorption states to attribute mass fluxes.
• Quantified surface and non-surface diffusion components.

Main Results:

• Both surface and non-surface diffusivities exhibit a non-monotonic trend, increasing then decreasing with gas loading.
• Surface and non-surface diffusion behaviors diverge significantly with variations in temperature.
• Gas-substrate affinity strongly influences the distinct behaviors of surface and non-surface diffusion.

Conclusions:

• The developed numerical method successfully distinguishes between surface and non-surface diffusion mechanisms.
• Understanding these distinct diffusion modes is crucial for optimizing gas transport in nanoporous materials.
• The study highlights the complex interplay between gas loading, temperature, and material properties on diffusion.