Computer simulations of hydrogen adsorption on graphite nanofibers

Adsorption of hydrogen on graphitic nanofibers has been computed from Grand Canonical Monte Carlo simulations. The graphite platelet spacing has been optimized to maximize the weight fraction of hydrogen adsorbed. Comparison of experimental data of Rodriguez and co-workers (Chambers, A; Park, C.; Ba ker, R. T. K.; Rodriguez, N. M. J. Phys. Chem. B 1998, 102, 4253) with adso rption isotherms from simulations indicate that the phenomenal uptake obser ved from experiments cannot be explained in terms of reasonable solid-fluid potentials. We have varied the strength and range of the solid-fluid poten tial in order to reproduce the experimental excess adsorption. If the form of the potential is held constant, the potential well depth must be increas ed by a factor of about 150 in order to reach the experimental data. If the range of the attractive well is allowed to increase from r(-6) to r(-4), t he potential well depth must be increased by about a factor of 30 to match experimental data. Given the magnitude of the well depths, we conclude that no physically realistic graphite-hydrogen potential can account for the ad sorption reported by Rodriguez et al.