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Résumé:

Hydrogen is widely considered an essential part of our energy future despite the substantial difficulties derived from its low volumetric energy density. The development of a suitable material for reversible storage of hydrogen still remains a 'grand challenge', in particular for vehicular applications. Although some materials are potentially attractive, even the most promising candidates have yet to meet the U.S. Department of Energy (DOE) 2010 targets (0.045 kg H2/kg system, 28 kg H2/m3 system at room temperature for light-duty vehicles).Carbons are one of potentially promising groups of materials for hydrogen storage by adsorption. However, the heat of hydrogen physisorption in such materials is low, in the range of about 4-8 kJ/mol which limits the total amount of hydrogen adsorbed at P = 100 bar to ~2 wt% at room temperature and about ~10 wt% at 77 K. To improve the sorption characteristics the adsorbing surfaces must be modified either by substitution of some atoms in the all-carbon skeleton by other elements, or by doping/intercalation with other species. We present ab initio calculations and Monte Carlo simulations showing that substitution of 5-10% of atoms in a nanoporous carbon by boron atoms results in significant increases of the adsorption energy (up to 10-13.5 kJ/mol) and storage capacity (~ 5 wt. % at 298 K, 100 bar) with a 97 % delivery rate. We analyze different possible mechanism of including boron atoms in the carbon structure: substitution and doping. We show how random distribution of boron modifies the energy landscape of interaction energy and mechanism of adsorption.