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Résumé:

Carbons are one of several promising groups of materials for hydrogen storage by ad-sorption. Here it is shown how appropriately engineered nanoporous carbons provide materials for reversible hydrogen storage storage capacities ~ 80 g H2/kg carbon, ~ 50 g H2/liter carbon at 50 bar and 77 K. The nanopores generate high storage capacities by having very large surfaces for adsorption, and by hosting deep potential wells for narrow pores. Experimental studies are presented with surface areas as high as 3100 m2/g, in which 40% of all surface sites reside in pores of width ~ 0.7 nm and binding energy ~ 9 kJ/mol, and 60% of sites in pores of width > 1.0 nm and binding energy ~ 5 kJ/mol. The prevalence of two binding energies is also in agreement with results from computer simulations. We also compare experimental and theoretical calculations of distinct models for the adsorption where molecules adsorb to discrete sites (localized adsorption) and where molecules are able to freely move in the adsorption plane (mo-bile adsorption) and explore the regimes in which the quantum nature of H2’s rotational degrees of freedom plays an important role.