CO2 adsorption by nitrogen-doped carbon nanotubes predicted by density-functional theory with dispersion-correcting potentials

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.