Hydrogen Storage in Carbon SWNTs: Atomic or Molecular?

Abstract

The atomistic nature of hydrogen storage in carbon SWNTs has been investigated by thermal desorption spectroscopy utilizing mass spectrometry. The partial pressures of desorbed H2, D2 and HD have been simultaneously recorded after sample loading with a 1:1 mixture of H2 and D2 gases. The amount of desorbed HD molecules approaches the ratio 2:1:1 for HD:H2:D2 in the case of atomic storage. In the case of molecular storage the concentration of HD approaches the background level. It was found that hydrogen isotopes are stored as atoms in SWNT samples containing transition metals from either sample production (Ni, Fe, …) and/or activation (opening) process (Ni, Fe, Ti, …). Purified SWNTs store hydrogen in the molecular state, if any.