Hydrogen adsorption in microporous alkali-doped carbons (activated carbon and single wall nanotubes)

Abstract

Adsorption of hydrogen gas was tested in microporous doped carbons: activated carbon (1600 m 2/g) and single wall carbon nanotubes (SWNTs). The isotherms of adsorption of LiC 18 and KC 24 doped microporous activated carbons were determined in the range [0–30 bar] at room temperature and 77 K. The chemisorption ratio observed at room temperature increases with increasing the alkali/carbon rate. The isotherm profiles of doped activated carbon at 77 K show no clear enhancement of the sorption ratio compared to the raw activated carbon. The adsorption sites of potassium doped SWNTs with closed end were determined by neutron diffraction experiment using deuterium gas. The K-doped SWNTs were found only slightly intercalated by K ions so that empty cavities are preserved in between the tubes. At room temperature, the chemisorption of deuterium was not observed in doped SWNTs bundles, but only in the KC 8 graphite intercalation compound impurities. At low temperature, the isotherms analysis and neutron diffraction experiments have shown that D 2 molecules are physisorbed in the free interstitial voids in between the tubes within the bundles.