F-, Cl-, Li+ and Na+ adsorption on AlN nanotube surface: A DFT study

Adsorption of two anions (F- and Cl-) and two cations (Li+ and Na+) on the surface of aluminum nitride nanotubes (AlNNTs) is investigated by density functional theory. The reactions are site-selective, so that the cations and anions prefer to be adsorbed atop the N and Al atoms of the tube surface, respectively. The adsorption energies of anions (-4.46 eV for F- and -1.12 eV for Cl-) are much higher than those of cations (about -0.17 eV for Li+ and -0.12 eV for Na+) which can be explained using frontier molecular orbital theory. It was found that the adsorption of anions may facilitate the electron emission from the AlNNT surface by reducing the work function due to the charge transfer occurs from the anions to the tube. It has been predicted that in contrast to the cations the adsorption of anions also obviously increases the electrical conductivity of AlNNT. (C) 2015 Elsevier B.V. All rights reserved.