Hydrogen storage capacity of Ti substitution-doped pyracylene: Density functional theory investigations

As candidates for hydrogen storage materials, Ti-doped pyracylenes, with a carbon atom replaced with a Ti atom, have been studied with density functional theory based method. Ti-doped pyracylene III with the Ti atom lying on a pentagon is the most stable isomer with substitutional energy of 4.73 eV/mol. Up to three H2 molecules can be adsorbed on to the Ti atom through charge transfer and partially chemisorptions due to the partially filled d orbitals and positive charges on Ti. Totally seven H2 molecules can be adsorbed on Ti-doped pyracylenes with mixture of chemo- and physisorption. Charge polarization induced electrostatic attraction is one of the major driving forces for physisorption.