Healing of a Vacancy Defect in a Single-Walled Carbon Nanotube by Carbon Monoxide Disproportionation

We propose a new mechanism for the bimolecular healing of the vacancy defect in single-walled carbon nanotubes (SWCNTs). The mechanism is of particular importance to avoid the errors often encountered in the electronic properties of carbon nanotubes. Using density functional theory (DFT) calculations with the Perdew-Burke-Ernzerhof (PBE) functional, we investigate the reaction mechanism of the healing process of the monatomic vacancy defect in the (8,0) SWCNT via carbon monoxide disproportionation. It is found that the proposed mechanism is theoretically possible and it has the following advantages: (1) The activation energy is only 9.37 kcal.mol(-1) for the 4-membered-ring-opening step at high CO concentrations; (2) no catalyst is needed, and thus no purification step is needed to remove the catalyst; (3) the CO can be used as a reactant; (4) no oxygen byproduct is found; and (5) there is a high selectivity of CO for vacancy defect sites. Our finding establishes that a CNT with a vacancy defect, as it is generally obtained from the syntheses or from uses as a nanomaterial device, can be healed completely and resumes its function as a perfect CNT displaying the original electronic properties.