CO2adsorption by nitrogen-doped carbon nanotubes predicted by density-functional theory with dispersion-correcting potentials

Abstract

The interaction of CO₂ to the interior and exterior walls of pristine and nitrogen-doped single-walled carbon nanotubes (SWNT) has been studied using density-functional theory with dispersion-correcting potentials (DCPs). Our calculations predict Gibbs energies of binding between SWNT and CO₂ of up to 9.1 kcal mol⁻¹, with strongest binding observed for a zigzag [10,0] nanotube, compared to armchair [6,6] (8.3 kcal mol⁻¹) and chiral [8,4] (7.0 kcal mol⁻¹). Doping of the [10,0] tube with nitrogen increases the Gibbs energies of binding of CO₂ by ca. 3 kcal mol⁻¹, but slightly reduced binding is found when [6,6] and [8,4] SWNT are doped in similar fashion. The Gibbs energy of binding of CO₂ to the exterior of the tubes is quite small compared to the binding that occurs inside the tubes. These findings suggest that the zigzag SWNT show greater promise as a means of CO₂ gas-capture.