Quantum effects on adsorption isotherm of hydrogen in strongly confining twisted carbon nanotubes

Hydrogen molecules that are confined in twisted single-wall carbon nanotubes act as a quantum fluid at low temperature. This work computes the adsorption thermodynamics of hydrogen that is stored in torsional single-walled carbon nanotubes, which is expected to increase the surface area of and structure stiffness of the nanotubes. Interestingly, the unique rifling nanostructure of these nanotubes strengthens the quantum effect. Simulation results reveal that the hydrogen storage capacity of slightly twisted single-wall carbon nanotubes exceeds that of pristine single-wall carbon nanotubes under the same adsorption conditions. The hydrogen molecules undergo quantum effect when the characteristic pore diameter is smaller than 3 nm. An insufficient pore size reduces the hydrogen storage density to an extent that depends on the azimuthal angle of twisted CNTs. From the simulations, the hydrogen adsorption capacity importantly depends on the twisted nanostructure, especially at 77 K. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.