Effect of Ge-doping on the adsorption of anions (F−, Cl−, Br−) onto the outer surface of boron nitride nanotube: a DFT study

In this study, the adsorption behavior of anions (F⁻, Cl⁻, Br⁻) on the surface of the single-walled boron nitride nanotube (SWBNNT) is explored using density functional theory (DFT). The interaction between the ions with the pristine BNNT and the Ge-doped BNNT is performed in the solution phase. According to the obtained data, the F⁻@BNNT and F⁻@Ge-BNNT systems have the highest adsorption energy with values of − 329.85 and − 344.71 kJ/mol, respectively. On the other hand, the lowest values have been shown in Cl⁻@BNNT and Cl⁻@Ge-BNNT structures with values of − 31.17 and − 57.79 kJ/mol, respectively. During the complexation, a decrease in the energy gap (E_g) is accompanied by an increase in the reactivity and electrical conductivity. The HOMO–LUMO energy gaps are found to be the lowest in F⁻@Ge-BNNT with 5.311 eV followed by Cl⁻@Ge-BNNT and Br⁻@Ge-BNNT with 5.299 eV and 5.293 eV, respectively, while these values are 8.028, 8.048, and 7.992 eV for F⁻@BNNT, Cl⁻@BNNT and Br⁻@BNNT, respectively. The intermolecular interactions between the species are also evaluated using the natural bond orbital (NBO) analysis. Finally, to confirm the obtained results, the calculated density of states is depicted.