Prediction of energetically optimal single-walled carbon nanotubes for hydrogen physisorption

Hydrogen storage by carbon nanotubes (CNTs) is a challenging issue still in debate. Using an approximate density functional method augmented with a van der Waals dispersion term, we have shown that there are binding maxima for H-2/single-walled carbon nanotube (SWCNT) complexes at (5, 5) and (8, 0) tubes for armchair and zigzag CNTs, respectively, with binding energies around three times as large as that of H-2 on graphene surface. We predict that SWCNTs with diameters of 6-7 angstrom are energetically optimal candidates for physisorption of molecular hydrogen. c 2009 American Institute of Physics. [DOI: 10.1063/1.3158597]