A catalyst-free achieving of N-doped carbon nanotubes: The healing of single-vacancy defects by NO molecule

Highlights: • A catalyst-free approach is suggested for achieving nitrogen-doped carbon nanotubes. • The healing of single-vacancy defects in carbon nanotubes is studies by means of NO molecule. • The recombination of NO molecule over the defective site is the rate-limiting step. • The large-radius defective carbon nanotubes with a small curvature are preferred for the healing with the NO molecule. Density functional theory calculations are performed to study the healing mechanism of single-vacancy defects in zigzag (n,0) CNTs by NO molecule (n = 6,8,10). The results indicate that the healing process proceeds through a two-step mechanism. First, NO molecule adsorbs over the defective site. Then, the extra oxygen atom (O_ads) is eliminated by three different ways: (i) NO + O_ads → NO₂, (ii) CO + O_ads → CO₂, or (iii) SO₂ + O_ads → SO₃. The dependency of the healing process on the tube diameter is studied in detail. The results of this work suggest a novel approach to achieve N-doped CNTs.