title: Influence of Structural Heterogeneity on Diffusion of CH4and CO2in Silicon Carbide-Derived Nanoporous Carbon.
abstract: We investigate the influence of structural heterogeneity on the transport properties of simple gases in a Hybrid Reverse Monte Carlo (HRMC) constructed model of silicon carbide-derived carbon (SiC-DC). The energy landscape of the system is determined based on free energy analysis of the atomistic model. The overall energy barriers of the system for different gases are computed along with important properties, such as Henry constant and differential enthalpy of adsorption at infinite dilution, and indicate hydrophobicity of the SiC-DC structure and its affinity for CO2and CH4adsorption. We also study the effect of molecular geometry, pore structure and energy heterogeneity considering different hopping scenarios for diffusion of CO2and CH4through ultramicropores using the Nudged Elastic Band (NEB) method. It is shown that the energy barrier of a hopping molecule is very sensitive to the shape of the pore entry. We provide evidence for the influence of structural heterogeneity on self-diffusivity of methane and carbon dioxide using molecular dynamics simulation, based on a maximum in the variation of self-diffusivity with loading. A comparison of the MD simulation results with self-diffusivities from quasi-elastic neutron scattering (QENS) measurements and, with macroscopic uptake-based low-density transport coefficients, reveals the existence of internal barriers not captured in MD simulation and QENS experiments. Nevertheless, the simulation and macroscopic uptake-based diffusion coefficients agree within a factor of 2-3, indicating that our HRMC model structure captures most of the important energy barriers affecting the transport of CH4in the nanostructure of SiC-DC.
authors.affiliation: School of Chemical Engineering, The University of Queensland , QLD 4072, Australia.
authors.forename: Amir H
authors.initials: AH
authors.lastname: Farmahini
authors.affiliation: School of Chemical Engineering, The University of Queensland , QLD 4072, Australia.
authors.forename: Ali
authors.initials: A
authors.lastname: Shahtalebi
authors.affiliation: Institut de Recherches sur la Catalyse et l'Environnement de Lyon, CNRS, Université Lyon 1 , 2 Ave. Albert Einstein, 69626 Villeurbanne, France.
authors.forename: Hervé
authors.initials: H
authors.lastname: Jobic
authors.affiliation: School of Chemical Engineering, The University of Queensland , QLD 4072, Australia.
authors.forename: Suresh K
authors.initials: SK
authors.lastname: Bhatia