Isotopic and spin selectivity of H_2 adsorbed in bundles of carbon nanotubes

TL;DR

This study investigates how hydrogen isotopes and spin states are preferentially adsorbed in carbon nanotube bundles, revealing significant selectivity that could be useful for gas separation technologies.

Contribution

It provides the first detailed calculations of isotope and spin selectivity of H_2 and D_2 in nanotube bundles, aligning with recent experimental findings.

Findings

Substantial spin selectivity up to 100 K

Greater isotope selectivity up to 300 K

Consistent with experimental isosteric heat differences

Abstract

Due to its large surface area and strongly attractive potential, a bundle of carbon nanotubes is an ideal substrate material for gas storage. In addition, adsorption in nanotubes can be exploited in order to separate the components of a mixture. In this paper, we investigate the preferential adsorption of D_2 versus H_2(isotope selectivity) and of ortho versus para(spin selectivity) molecules confined in the one-dimensional grooves and interstitial channels of carbon nanotube bundles. We perform selectivity calculations in the low coverage regime, neglecting interactions between adsorbate molecules. We find substantial spin selectivity for a range of temperatures up to 100 K, and even greater isotope selectivity for an extended range of temperatures,up to 300 K. This isotope selectivity is consistent with recent experimental data, which exhibit a large difference between the isosteric heats of D_2 and H_2 adsorbed in these bundles.