Résumé
One of the potentially promising porous structures for efficient hydrogen storage for mobile applications are carbon-based materials. However, the heat of hydrogen physisorption in pure porous carbons is low, in the range of about 4-8 kJ/mol. Consequently, the total amount of the adsorbed hydrogen cannot meet the DOE goals. To get better storage capacity, the adsorbing surfaces must be modified, either by substitution of a part of atoms in the all-carbon skeleton by other elements, or by doping/intercalation with other species. Such modifications lead to surfaces which are most probably, strongly heterogeneous. Here, we present Monte Carlo simulations of adsorption of molecular hydrogen in such modified carbon-based heterogeneous porous materials. We show that partial substitution of carbons (here, by boron) modifies the symmetry of the energy landscape and increases the strength of hydrogen physisorption on graphite. We discuss the consequences of such substitution on both the hydrogen uptake and adsorption mechanism. We extend our analysis on the influence of the size of slit-shape pores on the hydrogen uptake and show that, if carefully engineered, graphite-based sorbents can reach 2010 DOE requirements for hydrogen storage.