Electronic structures and bonding properties of chlorine-treated nitrogenated carbon nanotubes: X-ray absorption and scanning photoelectron microscopy studies

The electronic and bonding properties of nitrogenated carbon nanotubes (N-CNTs) exposed to chlorine plasma were investigated using C and N $K$-edge x-ray absorption near-edge structure (XANES) and scanning photoelectron microscopy (SPEM). The C and N $K$-edge XANES spectra of chlorine-treated N-CNTs consistently reveal the formation of pyridinelike N-CNTs by the observation of $1s→π*(e2u)$ antibonding and $1s→π*(b2g)$ bonding states. The valence-band photoemission spectra obtained from SPEM images indicate that chlorination of the nanotubes enhances the C–N bonding. First-principles calculations of the partial densities of states in conjunction with C $K$-edge XANES data identify the presence of C–Cl bonding in chlorine treated N-CNTs.