Hydrogen adsorption and storage in carbon nanotubes

A comprehensive studies on hydrogen adsorption and storage in carbon nanotu bes (CNTs) have been done both experimentally and theoretically. Hydrogen a toms have been stood electrochemically in CNTs. We find that hydrogens exis t as a form of H-2 molecule in an empty space inside CNTs, which was confir med by Raman spectra. Several adsorption sites in/on CNTs are observed duri ng the discharging process. We perform density-functional-based tight-bindi ng calculations to search for adsorption sites and predict maximum hydrogen storage capacity. Our calculations show that the storage capacity of hydro gen, limited by the repulsive forces between Hz molecules inside nanotubes, increases linearly with tube diameters in single-walled nanotubes, whereas this value is independent of tube diameters in multi-walled nanotubes. We predict that H storage capacity in (10,10) nanotubes can exceed 14 wt.% (16 0 kg H-2/m(3)). (C) 2000 Elsevier Science S.A. All rights reserved.