Hf decorated graphene for hydrogen storage: A first principles approach.

In the present investigation we performed density functional theory (DFT) calculations to study adsorption and binding energies, density of states (DOS) for pristine graphene, Hafnium (Hf) decorated graphene and hydrogen molecule (1H2−6H2) adsorbed on Hf-decorated graphene as well. We found adsorption energy in negative range -221.524 Ry for pristine graphene, after decorating Hf atom adsorption energy found -345.891 Ry. When we successively increase the hydrogen molecules (1H2−6H2) the adsorption energy decreases gradually, it ranging from (-348.197 Ry to -358.99 Ry). The binding energy per H2 molecule also decreases from 2.306 to 0.377 eV. The evaluated Fermi energies of studied system found in the range 1.089 eV to 3.928 eV. The successive increase in Fermi energy confirms the hydrogen molecules (1H2-6H2) have sufficient surface area of Hf decorated graphene. Our investigation reveals that Hf decorated graphene could be a promising material to store H2 molecules on a Hafnium (Hf) decorated graphene system. [ABSTRACT FROM AUTHOR]