Hydrogen adsorption and storage in carbon nanotubes

Abstract

A comprehensive studies on hydrogen adsorption and storage in carbon nanotubes (CNTs) have been done both experimentally and theoretically. Hydrogen atoms have been stored electrochemically in CNTs. We find that hydrogens exist as a form of H 2 molecule in an empty space inside CNTs, which was confirmed by Raman spectra. Several adsorption sites in/on CNTs are observed during the discharging process. We perform density-functional-based tight-binding calculations to search for adsorption sites and predict maximum hydrogen storage capacity. Our calculations show that the storage capacity of hydrogen, limited by the repulsive forces between H 2 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.% (160 kg H 2/m 3).