Comparative Study of Defect Reactivity in Graphene

We have applied dispersion corrected density functional theory to gauge the reactivity of the most common defects found in graphene. Specifically, we investigated single vacancies, 585 double vacancies, 555-777 reconstructed double vacancies, Stone- Wales defects, and hydrogenated zigzag and armchair edges. We found that the extent to which defects increase reactivity is strongly dependent on the (a) functional group to be attached and (b) number of functional groups attached. For the addition of one H, F, and phenyl groups to defective graphene, we found the following decreasing order of reactivity: single vacancy > hydrogenated zigzag edge > 585 double vacancy > 555-777 reconstructed double vacancy > Stone-Wales > hydrogenated armchair edge > perfect graphene. However, when two phenyl groups are attached, the Stone-Wales defect becomes more reactive than the 585 double vacancy and 555-777 reconstructed double vacancy. The largest increase of reactivity is observed for the functional groups whose binding energy onto perfect graphene is small. In contrast with recent experimental results, we determined that the reactivity of edges in comparison with perfect graphene is much higher than the reported value. When two groups are attached onto a 585, 555-777, or Stones-Wales defect, they prefer to be paired on the same CC bond on opposite sides of the sheet. However, for the single vacancy, this is not the observed behavior as the preferred addition sites are those carbon atoms that were previously bonded to the missing carbon.