Adsorbate-induced defect formation and annihilation on graphene and single-walled carbon nanotubes

We used density functional theory calculations to probe the chemical reactivity of graphene and single-wall carbon nanotubes (CNTs) toward the small molecules O(2), H(2), N(2), C(2)H(2), CO, and CO(2). We found that there is a threshold CNT size below which C(2)H(2) and CO, typical feedstock precursors for CNT growth, become trapped in decorated hillock-like defects on the side walls of CNTs. We also found that O(2), H(2), and CO(2) can etch isolated C adatoms and C adatom pairs. These processes play a role not only in the growth of CNTs, but also in the postgrowth evolution of defects on CNTs through exposure to typical ambient gases.