Density functional theory calculations were used to study the healing process of a defective carbon nanotube, a (8,0) carbon nanotube, by CO molecules. The healing underwent three evolutionary steps: chemisorption of the first CO molecule, incorporation of the C atom of CO into the carbon nanotube, accompanied by the adsorption of the leaving O atom on the carbon nanotube surface, and removal of the adsorbed O atom from the surface by a second CO molecule to form CO2 and a perfect carbon nanotube. Overall, adsorption of the first CO revealed a barrier of 2.99kcal/mol and was strongly exothermic (109.11kcal/mol) while adsorption of a second CO involved an intrinsic barrier of 32.37kcal/mol and was exothermic (62.34kcal/mol). In view of the unique conditions of carbon nanotube synthesis (high temperatures and a closed container), healing of the defective carbon nanotube could be effective in the presence of CO molecules. It was proposed that, among the available carbon nanotube synthesis procedures, the good performance of chemical vapor decomposition of CO on metal nanoparticles could be attributed to the dual role played by CO. That is, CO acted as both a carbon source and a defect-healer.

Theoretical Investigation of the Interaction Between Carbon Monoxide and Carbon Nanotubes with Single-Vacancy Defects. B.Xiao, J.Zhao, Y.H.Ding, C.C.Sun: ChemPhysChem, 2010, 11[16], 3505-10