Ab Initio Study of Boron- and Nitrogen-Doped Graphene and Carbon Nanotubes Functionalized with Carboxyl Groups

We study the mechanism of covalent functionalization of boron (B)- and nitrogen (N)-doped graphene and carbon nanotubes by carboxyl (COOH) groups. Our calculations are carried out using an ab initio density functional pseudopotential computational method combined with the generalized gradient approximation for the exchange-correlation functional. The binding energies and equilibrium structures of carboxylated B/N-doped graphene sheets and carbon nanotubes are examined in cases of graphene and nanotubes containing no surface defects, containing Stone Wales defects, and containing vacancies. We find that B doping increases and N doping decreases the binding energy of COOH groups to defect-free and defective graphene and carbon nanotubes. This result suggests that substitutional doping may significantly alter the surface reactivity of carbon nanomaterials.