Adsorption of nitrogen oxides on Al-doped carbon nanotubes: the first principles study

Abstract

The first principles calculations were performed to study the adsorption of NO/NO2 molecules on carbon nanotubes (CNTs) doped with different number of aluminum atoms. Calculations show that upon the aluminum doping, the adsorption distance is decreased while the charge density, adsorption energy and charge transfer are increased dramatically, indicating that the adsorption of NO/NO2 on CNTs could be greatly enhanced. The analysis of frontier orbit and density of states suggests that Al doping reduces the energy gap and increases the conductivity of CNTs. The density of states of Al-doped CNTs and NO/NO2 molecules are significantly improved at the Fermi level, which results in strong coupling between CNTs and NO/NO2 molecules and the increase of the adsorption of NO/NO2. In addition, results show that increasing the number of doped Al atoms lead to stronger adsorption of NO/NO2 on CNTs. The adsorption of NO2 on CNTs, on the other hand, is slightly stronger than NO in all the cases studied in this paper.