Molecular Dynamics Study of CO2/H2 and CH4/H2 Gas Separation by Nanoporous Graphene

Abstract

Abstract The combustion of coal produces CO2 emissions, rising greenhouse gas levels, and leading to global warming. Hydrogen is one potential clean source of energy. However, current hydrogen production methods produce CO and CO2 emissions, while pure hydrogen is required for fuel cells. Therefore, efficient methods for capturing greenhouse gases and the extraction of pure hydrogen are required. Membrane gas separation requires low energy and cost. However, current polymer-based membranes struggle with the trade-off between selectivity and permeability. Graphene-based membranes like nanoporous graphene (NPG) are potential candidates due to its monoatomic thickness and high mechanical performance, offering high permeability. Selectivity was altered by controlling the nanopore shape, size, and functionality, and using multi-layered NPG with various interlayer spacing and angle. Molecular dynamics simulations were performed to study the transport phenomena for graphene-based membrane gas separation. CO2/H2 and CH4/H2 gas mixtures separation were performed on a bottom-up synthesized H-Passivated NPG with Dumbbell-Shaped Nanopores. Results show that 100% H2 selectivity was achieved for both CH4/H2 and CO2/H2 gas mixtures, using single layer NPG and tri-layer NPG, respectively, while maintaining high permeability in the order of 105-106 GPU. Therefore, the H-Passivated NPG with Dumbbell-Shaped Nanopores is an excellent choice of membrane for gas separation.