Defect-induced chemisorption of nitrogen oxides on (10,0) single-walled carbon nanotubes: Insights from density functional calculations

The interactions of NOx (x=1,2,3) with the defective semiconducting (10,0) carbon nanotubes were studied by the density functional theory. Optimized geometries, binding energies, and electronic structures of the NOx-adsorbed nanotubes were determined on the basis of calculations. Effects of the defect density and the electric field on the binding energy and charge transfer have been investigated. In sharp contrast with the case of perfect nanotube, the adsorption of NOx at the defect site of (10,0) tube is generally chemical, and after the chemisorption of one NO2 or one NO3 the carbon nanotubes with various defects behave as conductors, while the consecutive adsorption of the second NO2 or the second NO3 makes these tubes become semiconductors again. Calculations show that the NO2 adsorption at a topological defect is a barrier-free process, while the NO3 adsorption experiences a barrier due to transition of the π↔s electronic configuration of the NO3 moiety.