Hydrogen storage in carbon nanotubes and graphitic nanofibers

We review experiments and computer simulations of adsorption of hydrogen on carbon nanotubes and on graphitic nanofibers. New results for adsorption of hydrogen on bundles of nanotubes intercalated with alkali metals are presented. The size and charge of the metal clusters is explicitly accounted for through a simple model. Charge transfer of electrons from the metal clusters to the nanotubes is also modeled. Results indicate that adsorption of hydrogen in metal-intercalated nanotube bundles is substantially enhanced compared with adsorption onto pure nanotubes. We compare simulations of adsorption in bundles with various lattice spacings to experimental results that claim swelling of nanotube bundles by adsorption of hydrogen. We find good agreement between the simulations and the experiments at higher pressures, indicating that hydrogen at 80 K probably does intercalate and swell nanotube bundles, thereby increasing the capacity of the sorbent. (C) 2002 Elsevier Science B.V. All rights reserved.