Gas molecule adsorption in carbon nanotubes and nanotube bundles

TLDR

Using first‑principles calculations, we examined NO₂, O₂, NH₃, N₂, CO₂, CH₄, H₂O, H₂, and Ar adsorption on single‑walled carbon nanotubes and bundles, determining equilibrium positions, adsorption energies, charge transfer, and electronic band structures for various SWNTs. We found that most gases adsorb weakly on individual SWNTs as charge donors or acceptors, but adsorption is stronger at bundle interstitial and groove sites, with NO₂ and O₂ significantly altering electronic properties and charge transfer potentially affecting transport, in agreement with recent experiments.

Abstract

We studied various gas molecules (NO2, O2, NH3, N2, CO2, CH4, H2O, H2, Ar) on single-walled carbon nanotubes (SWNTs) and bundles using first principles methods. The equilibrium position, adsorption energy, charge transfer, and electronic band structures are obtained for different kinds of SWNTs. Most molecules adsorb weakly on SWNTs and can be either charge donors or acceptors to the nanotubes. We find that the gas adsorption on the bundle interstitial and groove sites is stronger than that on individual nanotubes. The electronic properties of SWNTs are sensitive to the adsorption of certain gases such as NO2 and O2. Charge transfer and gas-induced charge fluctuation might significantly affect the transport properties of SWNTs. Our theoretical results are consistent with recent experiments.