Hydrogen storage mechanism of multiwalled carbon nanotube bundles studied by X-ray absorption spectra

Multiwalled carbon nanotube bundles have been investigated with the near-edge X-ray absorption fine structure (NEXAFS) spectra. In the angle-dependent NEXAFS spectra of multiwalled carbon nanotube bundles, a change of the intensity of the C-H sigma* with the synchrotron radiation light incident angle has been observed. The presence of the C-H bond at room temperature and ambient pressure may be related to the defects in the carbon nanotubes. Neither the C-C pi* nor the C-C sigma* is similar to the C-H sigma*, which strongly suggests that the hydrogen atoms are adsorbed on the defects on the interior surface of the wall of carbon nanotubes at room temperature and ambient pressure. These results indicate that NEXAFS spectrum is a powerful tool for the investigation of multiwalled carbon nanotube bundles.