Combined experimental and computational studies have been performed to understand the effects of singlewalled carbon nanotube (SWNT) diameter and chirality on the heat of adsorption of hydrogen and the hydrogen storage capacities at near-ambient temperatures. As part of these studies, a force field methodology has been developed for the description of carbon-carbon and carbon-molecular hydrogen interactions that is ideally suited to modeling hydrogen adsorption on SWNT [1]. This approach has been used in molecular dynamics (MD) simulations for hydrogen adsorption in SWNT. The results reveal significant nanotube deformations, consistent with previous ab initio MD simulations [2], and the calculated energies of adsorption at ambient temperature are comparable to the reported experimental activation energies of desorption for H2 in SWNT [3,4] and the isosteric heat of adsorption calculated from high pressure adsorption isotherms measured in our laboratories. Our combined experimental and computational studies show that SWNT physical dimensions (diameter, aspect ratio) and have a substantial effect on the energies of adsorption and hydrogen capacities. The prospects for achieving the U.S. Department of Energy targets for gravimetric and volumetric hydrogen storage capacities using adsorption on SWNT will be discussed.

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