GCMC simulation of hydrogen adsorption in densely packed arrays of Li-doped and hydrogenated carbon nanotubes

The upper threshold of hydrogen adsorption in Li-doped and hydrogenated carbon nanotube densely packed arrays is calculated to check the ability of such systems to fulfill the target indicated by the United States Department of Energy (DOE). To this aim, model potential parameters have been obtained by Density Functional Theory and have been used to calculate the adsorption isotherms in honeycomb arrays containing up to seven tubes by means of Grand-Canonical Monte Carlo simulations. A hybrid model has been developed involving both atomistic potentials for short-range interactions and integrated potentials for hydrogen interacting with distant tubes. In the pressure range explored, it is shown that the hydrogen adsorption performances of Li-doped carbon nanotubes arranged in close packed honeycomb arrays, while being enhanced with respect to pristine carbon nanotubes, are still well below the DOE targets.