Isosteric Heats of Adsorption in the Henry's Law Region for Carbon Cylindrical Nanopores and Spherical Nanocavities

The isosteric heat of adsorption in the Henry's law region is calculated as a function of pore width for a molecule adsorbed in a carbon cylindrical nanopore and in a carbon spherical nanocavity. These geometries are models for a single-wall carbon nanotube (SWNT) and fullerene (C60). The maximum isosteric heat of adsorption is obtained for six gas molecules: argon, methane, carbon dioxide, hydrogen, helium, and nitrogen. In addition, the results for the cylindrical nanopore are compared with adsorption data from the literature for a SWNT. We determine the pore width where the isosteric heat of adsorption is a maximum for each of the geometries. Constant relationships between the pore diameters for the maximum isosteric heat of adsorption and the specific solid-fluid Lennard-Jones (LJ) parameters are found for cylindrical nanopores, spherical nanocavities, and parallel-wall slit-shaped pores. Surface mean curvature has a significant influence on the isosteric heat of adsorption.