Selective adsorption of carbon dioxide from mixed vapors by blockage of methane in graphene nanoribbons

Abstract

We study numerically the adsorption of a mixture of $$\hbox {CO}_{2}$$ and $$\hbox {CH}_{4}$$ on a graphite substrate covered by graphene nanoribbons (NRs). The NRs are flat and parallel to the graphite surface, at a variable distance ranging from 6 to 14 A. We show that the NRs-graphite substrate acts as an effective filter for $$\hbox {CO}_{2}$$ . Our study is based on molecular dynamics simulations. Methane is considered a spherical molecule, and carbon dioxide is represented as a linear rigid body. Graphite is modeled as a continuous material, while the NRs are approached atomistically. We observe that when the NRs are placed 6 A above the graphite surface, methane is blocked out, while $$\hbox {CO}_{2}$$ molecules can diffuse and be collected in between the NRs and the graphite surface. Consequently, the selectivity of $$\hbox {CO}_{2}$$ is extremely high. We also observe that the initial rate of adsorption of $$\hbox {CO}_{2}$$ is much higher than $$\hbox {CH}_{4}$$ . Overall we show that the filter can be optimized by controlling the gap between NRs and the NRs-graphite separation.