CO₂ Adsorption on Charged Carbon Nanotube Arrays: A Possible Functional Material for Electric Swing Adsorption

The adsorption and orientational ordering of carbon dioxide molecules on parallel bundles of charged as well as uncharged carbon nanotubes were investigated at 300 K using grand canonical Monte Carlo and molecular dynamics. Zigzag and armchair single-walled carbon nanotubes of radius ∼1.5 nm and different intertube distances between 0 and 2 nm were used. A fixed charge of 0.01–0.04 e was placed on each carbon to investigate the effect of charge. Adding a positive charge to the carbon nanotubes causes a significant increase in adsorption (up to 35% at a pressure of 1.88 bar), while the gas adsorption decreases by up to 15% on negatively charged carbon nanotubes. The increase or decrease of adsorption upon charging is attributed to the change in potential energy for the interaction between the individual carbon dioxide molecule and the nanotube. The higher adsorption on positively charged nanotubes leads to thicker adsorbed layers and a lower orientational order of the adsorbed molecules.