The physisorption of hydrogen on Single Walled Carbon Nanotubes (SWNTs) has been spectroscopically studied by Fourier Transform Infrared Spectroscopy at pressures up to 1000 psi and at ambient temperature.
A sample preparation technique has been developed to apply thin films of SWNTs to KBr or Si substrates. The samples showed a broad general absorption which increased with the amount of nanotubes, but it did not show any spectral evidence of the SWNTs or functional groups attached to the nanotubes.
It has been shown, that the broad absorption is due to scattering, which can be reduced by up to 50% by applying a refractive index matching liquid. Furthermore baking up to 700° C increases the transmission by up to 90%, which allows the observation of higher sample amounts.
Measurements at high pressure showed that the hydrogen dipole moment, induced by a perturbation of the electronic distribution of the H2 molecule due to physisorption on SWNTs, lies below the sensitivity of the system for samples of up to 2.1 mg of nanotubes.
At the introduction of hydrogen, water as an impurity of the hydrogen has been observed, which adsorbed on the sample surface. Also an increase in the gaseous CO2 has been detected, which can be caused by adsorped CO2 on the cell wall which is sputtered off by the impact of the hydrogen molecules at high pressure.M.S.Includes bibliographical references (p. 69-71)
