Heterosubstituted sumanene as media for hydrogen storage: A theoretical study

Recently, bowl-shaped pi-conjugated compounds, considered as carbon-based materials, have shown noticeable capacities in the hydrogen storage. Doping these compounds with appropriate elements remains the main target to improve the hydrogen adsorption properties. In this regards, we carried out a theoretical study, by means of MP2 method, on a series of mono-, di- and tri-heterosubstituted sumanene compounds, adsorbing hydrogen molecule from concave and from convex side, respectively. Benzylic carbons have been substituted by O, S, NH and NCH3 groups. The influence of this substitution on the adsorption properties has been reported. Our investigation has involved binding energies corrected to basis set superposition error (BSSE) and structural parameters like equilibrium distances as well as bowl depths. Dipole moment, HOMO-LUMO energy gap and the changes after the adsorption process have also been evaluated. The results show that the binding energy values belong to the range of the intermediate interval of physisorption mechanism. Natural population analysis (NPA) associated to natural bond orbitals (NBO) elucidate the charge transfer occurring between the heterosubstituted compounds and the hydrogen molecule. We classified the substituents upon the binding energy for mono-, di- and trisubstitution and no similarities have been reported between the adsorption sides. These classifications can be of interest to any prospective experimental investigation. (c) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.