A density function theory (DFT) is applied to investigate the interaction and adsorption of nitrate ion on the exterior and interior surface of the pristine, Al and Ga-doped BNNTs. The calculated results indicate that the values of adsorption energy and enthalpy of the NO3 −@ Al-doped BNNTs complex is more negative than pristine and Ga-doped. The adsorption energy nitrate ion on the surface of BNNTs is in order Al-doped > Ga-doped > pristine. This result demonstrates that the adsorption of nitrate ion on the surface of Al-doped BNNTs is stronger than Ga doped and pristine states. The chemical potential (μ) values for nitrate ion adsorption on the pristine, Al and Ga doped BNNTs are negative and is in order μpristine > μAl-doped > μGa-doped, it means that these compounds are stable. The values of ▽2ρ(BCP) and H( BCP) for [(NO3)O…B(BNNTs)] at the all adsorption models are positive and the |V/G| ratio for all models is > 2, it denotes the strong electrostatic interaction between nitrate ion with nanotube. In addition, the results of natural bonding orbital (NBO) and maximum charge transfer parameters (ΔN) indicate that at all adsorption models, the charge transfer occurs from nitrate ion toward nanotube and nanotube acts as p-type semiconductor.
