Calculations of hydrogen coverage on single-walled carbon nanotubes: Dependence on nanotube size, temperature, and pressure

We have investigated the stability of various hydrogenated single-walled carbon nanotubes. We find that the storage capacity of hydrogen depends significantly on the diameters of carbon nanotubes. Full hydrogen coverage can be reached for nanotubes with small size, while for nanotubes with large size, the saturation coverage is lower than 1. We have calculated the variation of the hydrogen coverage with the change of temperature and pressure. In particular, we find that nanotubes with diameters of about 10.3em0exnm can achieve a coverage of 80% at ambient temperature and low pressure, which is in agreement with the experimental results.