Hydrogen Physisorption on Carbon Foams upon Inclusion of Many-Body and Quantum Delocalization Effects

We investigate the effect of the structural characteristics of idealized nanoporous environments on the adsorption of molecular hydrogen. The storage capacities of the (n,n) armchair and zigzag carbon foams (n = 2-5) are evaluated in a broad range of thermodynamic conditions. Our calculations are performed within an extension of the density functional theory of liquids to quantum fluids at finite temperature (QLDFT) of particles obeying Bose-Einstein statistics. The exchange-correlation (excess) functional is derived from the empirical equation of state of the homogeneous system. Graphitic foams are found to exhibit hydrogen uptakes similar to other carbonaceous materials, the largest gravimetric capacity being that of the (5,5) zigzag structure (similar to 4.5% at T = 77 K). The storage properties show a rather smooth dependence on the size of the pore. The effects of the H-2-H-2 interactions on adsorption isotherms are evaluated via the comparison of QLDFT results with calculations based on the ideal gas approximation.