Nitrogen physisorption and site blocking on single-walled carbon nanotubes

N2 physisorption on Single-Walled Carbon Nanotubes (SWCNTs) was investigated by cryogenic thermal-desorption spectroscopy (cryo-TDS). TDS spectra revealed a desorption peak at 48 K (α) for as-purified SWCNTs and an additional desorption peak at 73 K (β) for air-oxidized SWCNTs. When N2 and H2 were coadsorbed on SWCNTs, H2 adsorption was blocked by the N2 preadsorption. By comparing the TDS data with and without the N2 preadsorption, the α and β peaks were attributed to N2 adsorbed on the groove site and inside of SWCNTs, respectively.