Adsorption of H2 and D2 on Carbon Nanotube Bundles

Adsorption isotherms of H2 and D2 deposited on single wall, closed end carbon nanotube bundles have been measured. Two temperature ranges were covered, a) T>77 K to study adsorption on high energy binding sites, and b) T<45 K to characterize adsorption on the graphite-like (graphene) outside surface of the bundles. For reference, N2 and Ar isotherms were measured at T>77 K. We observe two well defined steps in the isotherms that correspond to adsorption on at least two distinct locations, grooves/interstitials and the graphene surface. The calculated isosteric heats of adsorption, Qst, in the grooves/interstitials are approximately twice the value on the graphene.