Methane storage on aluminum-doped single wall BNNTs

Abstract

• Al-doped BNNTs with N atoms replaced by Al can be treated as a good medium for storage and also a sensor for methane detection. • Each Al-site is only able to absorb one CH 4 molecule. • At low concentration of Al atoms in the surface of BNNTs, the adsorption and gas sensor properties of the Al-doped BNNTs with respect to CH 4 remain unchanged. Adsorption of methane (CH 4 ) on inside and outside of aluminum-doped (Al-doped) zigzag single-walled boron nitride nanotubes, BNNTs/Al, has been studied using density-functional theory (DFT) method. The effect of diameter and type of atom of BNNT replaced by the Al atom on the adsorption properties of CH 4 were investigated. Our results indicate that, compared to pristine BNNTs, replacing both B atom by Al, BNNT/Al(B) and N atom by Al, BNNT/Al(N), can notably enhance the binding energy of CH 4 on BNNTs and the latter case has been more superior. The average binding energy for the most stable configuration of CH 4 on BNNTs/Al(N) and BNNTs/Al(B) are about −26.12 and −16.53 kJ mol −1 , respectively, which are typical for the physisorption and suitable for technical applications. The results show that while the geometry of BNNT/Al(N or B)–CH 4 complexes is determined by weak electrostatic forces, the binding energy mainly determines by dispersion forces. For all complexes, the energy gaps, natural bond orbital (NBO) analysis, dipole moments, natural charge and density of state (DOS) diagrams were extracted. Finally, the applicability of BNNTs/Al(N) both as a medium for storage and gas sensor for methane detection were confirmed.