A comparative study on hydrogen interaction with defective graphene structures doped by transition metals

• Interaction of H2 molecules with defective graphene doped TM atoms was studied.
• 585 divacancy-TM had the strongest binding energy compared to SW and 555-777.
• 555-777 structure doped by Sc had the maximum capacity for hydrogen molecules.
• H2 binding energies on 555-777/Sc system were in the favorable range of 0.2–0.4 eV.

In the present work, the interaction of hydrogen molecules with defective graphene structures doped by transition metal (TM) atoms is investigated by using first principles density functional theory (DFT). Defective graphene structures include Stone–Wales (SW), 585 and 555-777 and transition metals include early TMs, i.e. scandium (Sc), titanium (Ti) and vanadium (V). It is found that in comparison with the pristine graphene, presence of defects significantly enhances the metal binding. Among three defects, 585 divacancy leads to the strongest binding between graphene and metal. Hydrogen adsorption is then evaluated by sequential addition of hydrogen molecules to the system. The results reveal that in comparison with other structures, 555-777 defective structure doped by Sc has the maximum capacity for hydrogen molecules. Also it is indicated that none of hydrogen molecules were dissociated during relaxation, indicating that all hydrogen molecules are accessible for reversible storage. Moreover, it is found that binding energies for adsorption of hydrogen molecules over 555-777/ Sc system are in the favorable range of 0.2–0.4 eV/H2.