Adsorption of H2 and D2 on carbon nanotube bundles

Adsorption isotherms of H-2 and D-2 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, N-2 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, Q(st), in the grooves/interstitials are approximately twice the value on the graphene.