The adsorption of molecular hydrogen gas onto charged single-walled carbon
nanotubes (SWNTs) is studied by grand canonical Monte Carlo (GCMC) computer
simulation. The quadrupole moment and induced dipole interaction of hydrog
en with "realistically" charged (0.1 e/C) nanotubes leads to an increase in
adsorption relative to the uncharged tubes of similar to 10%-20% for T = 2
98 K and 15%-30% for 77 K. Long-range electrostatic interactions makes seco
nd layer (exohedral) adsorption significantly higher. Hydrogen orientation-
ordering effects and adsorption anisotropy in the electrostatic field of th
e nanotube were observed. The geometry of nanotube arrays was optimized at
fixed values of charge, temperature, and pressure. In general, negatively c
harged nanotubes lead to more adsorption because the quadrupole moment of h
ydrogen is positive. Calculated isotherms indicate that even charged nanotu
be arrays are not suitable sorbents for achieving the DOE target for hydrog
en transportation and storage at normal temperatures, unless the charges on
the nanotubes are unrealistically large. (C) 1999 American Institute of Ph
ysics. [S0021-9606(99)71245-6].