Syngas Segregation Induced by Confinement in Carbon Nanotubes: A Combined First-Principles and Monte Carlo Study

A theoretical study combining first-principles and Monte Carlo simulations has been carried out to investigate the interactions of H 2 and CO molecules with carbon nanotube (CNT) surfaces. The results show that there are stronger interactions of both H 2 and CO with the interior nanotube surface than with the exterior surface. In addition, CO interacts more strongly with CNT surfaces than H 2 . This can be explained by the nature of the molecules and the different electronic properties of the concave and convex surfaces of CNTs formed by graphene layers. As a result, syngas molecules are enriched inside CNTs and the enrichment generally becomes greater in smaller nanotubes. Furthermore, the ratio of CO/H 2 inside CNTs increases with respect to the composition of syngas in the exterior gas phase. The enriched reactants and altered CO/H 2 ratio inside nanotubes could be beneficial for the reaction rate and lead to modification of the product selectivity.