Catalytically healing the Stone-Wales defects in graphene by carbon adatoms

Graphene with a perfect hexagonal network structure is desirable for various reasons, e.g., mechanical, thermal conductivity and transport properties. Yet, the embedded defects generated either in synthesis or usage stages have posed obstacles for graphene applications. Therefore, removal of the structural defects in graphene has remained an important task. Stone-Wales (SW) defects are one typical topological structure in the carbon nanomaterials. Unfortunately, the SW defects in graphene have to overcome a very high restoration barrier (ca. 6 eV). Very recent theoretical work has shown the promise to reduce the restoration barrier by the adsorbed transition metal atoms down to 2.86 eV (for W) (yet this is still too high). In the present density functional theory (DFT) study, we find that through a mechanically different process, the adsorption of carbon atoms can dramatically reduce the restoration barrier to hitherto the lowest value, i.e., 20.0 kcal mol(-1) (0.87 eV), which could make the SW-healing experimentally accessible. Subsequently, the C-adatom can migrate very easily on the graphene surface. As a result, one carbon adatom could principally catalyze the healing of all the SW defects in a cascade mode if no termination steps exist. During the graphene growth, the presently proposed carbon-adatom catalytic mechanism could have played a role in healing the SW defect. Moreover, we propose that in the post-treatment of graphene, adsorption of the carbon adatom could be used as an effective catalyst for the SW-healing. The catalytic role of carbon atoms on the SW defect should be included in the modeling of graphene growth.