Investigation of the pore structure of as-prepared and purified HiPco single-walled carbon nanotubes by N2/Ar adsorption -: Implication for H2 storage

Open single-walled carbon nanotubes (SWNTs) are attractive as potential storage media for hydrogen gas. The present paper investigates the micropore structure of HiPco SWNTs samples, as studied by nitrogen and argon adsorption technique at low pressures. The proportion of open SWNT is estimated with the Horvath-Kawazoe method. The results show that as-prepared samples may contain as much as 40% open SWNTs, whereas the oxidative purification process reduces this amount significantly. X-ray diffraction and Raman spectroscopy show that the Horvath-Kawazoe method is reliable for estimating the diameter of open SWNTs. In addition, the Horvath-Kawazoe method appears to be sensitive to species adsorbed in the outer grooves.