Grand Canonical Monte Carlo Simulations to Determine the Optimal Interlayer Distance of a Graphene Slit-Shaped Pore for Adsorption of Methane, Hydrogen and their Equimolar Mixture

Abstract

The adsorption—for separation, storage and transportation—of methane, hydrogen and their mixture is important for a sustainable energy consumption in present-day society. Graphene derivatives have proven to be very promising for such an application, yet for a good design a better understanding of the optimal pore size is needed. In this work, grand canonical Monte Carlo simulations, employing Improved Lennard–Jones potentials, are performed to determine the ideal interlayer distance for a slit-shaped graphene pore in a large pressure range. A detailed study of the adsorption behavior of methane, hydrogen and their equimolar mixture in different sizes of graphene pores is obtained through calculation of absolute and excess adsorption isotherms, isosteric heats and the selectivity. Moreover, a molecular picture is provided through z-density profiles at low and high pressure. It is found that an interlayer distance of about twice the van der Waals distance of the adsorbate is recommended to enhance the adsorbing ability. Furthermore, the graphene structures with slit-shaped pores were found to be very capable of adsorbing methane and separating methane from hydrogen in a mixture at reasonable working conditions (300 K and well below 15 atm).

Special Issue “Theoretical Calculation and Molecular Modeling of Nanomaterials”

“…A work employing grand canonical Monte Carlo simulations to investigate the adsorption behavior of methane, hydrogen, and their mixture in graphene pores of different sizes is also included. This study reveals that an interlayer distance approximately twice the van der Waals distance of the adsorbate enhances the adsorbing ability, and slit-shaped graphene pores demonstrate high adsorption capacity for methane and effective separation from hydrogen in a mixture at practical working conditions [12].…”

Development of accurate potentials for the physisorption of water on graphene

“…Therefore, in light of these new findings, in this work we aim to provide accurate but simple potentials obtained from first principle calculations, and able of adequately modelling the physisorption of water on graphene as we have done previously for methane 26 , nitrogen 27 and carbon monoxide 28 . These potentials have already been successfully applied in Molecular Dynamics and Monte Carlo simulations on adsorption and separation of gas mixtures on graphene 29,30 . The addition of this water force field brings within reach the simulation of realistic gas mixtures, which often contain methane, nitrogen, carbon monoxide and water.…”