Hydrogen storage capacity of bundles of single-walled carbon nanotubes with defects

We study the hydrogen storage capacity of bundles of single-walled carbon nanotubes (SWCNT) at 80 and 298K using molecular dynamics simulations. The effect of packing on the storage capacity of the bundles is studied using triangular and square arrays of nanotubes with various separation distance between adjacent nanotubes. The gravimetric storage capacity of the bundles increases with the separation distance between individual nanotubes. At low temperature, the storage capacity of bundles is significantly lower than for isolated SWCNT as the intertube distance is smaller than the adsorbed layer thickness of hydrogen. At high temperature, the adsorbed layer thickness corresponds to only a monolayer of hydrogen around SWCNTs, and hence, hydrogen is captured in the interstitial spaces within the bundle. As the groove volume in the square array is higher than that in the triangular array, the storage capacity of the bundle with square array is higher. An introduction of the Stone-Wales defects on the surface of nanotubes further increases the storage capacity of the bundle due to the higher binding energy of the 8-member rings of the defective SWCNTs. We also observe that more hydrogen molecules are packed in the interstitial spaces due to the deformation of the nanotubes caused by the presence of defective sites. Copyright (c) 2016 John Wiley & Sons, Ltd.