Nitrogen substitution and vacancy mediated scandium metal adsorption on carbon nanotubes

First-principle calculation reveals that N containing carbon nanotubes (CNTs) can support the functionalization of transition metals such as Sc on the CNT surface. For N-substituted CNTs without a vacancy, the enhanced adsorption results from large electron affinity difference of the N adjacent to C atom. In this case, the N atom activates nearby C atom and enhances its interaction with the Sc metal on the CNT surface. Meanwhile, the formation of a vacancy in CNTs causes local reconstruction of the surface near the vacancy site. Simulation and analysis show that vacancy mediated N substitution is a more favored scheme for Sc functionalization on the surface of CNTs that suppresses the clustering of Sc. The enhanced Sc adsorption in N-doped CNTs with mono- and di-vacancy defects was attributed to strong hybridization between the Scandium d orbital and nitrogen p orbital. The results explain theoretically the mechanism of enhanced functionalization of metals on N doped CNTs and suggests that Sc functionalized nitrogen doped CNTs with vacancies is an excellent candidate for the adsorption of small molecules.