Permeation selectivity of pristine and vacancy defected hexagonal boron membranes for alkaline earth metal and ions

Abstract

Permeation and selectivity of alkaline metal atoms and ions through normal and defected hexagonal boron nitride is explored in the presence and absence of water. The defects include one (V_B and V_N), two (V_BN) and three atoms (V_B(2N) and V_N(2B)) vacancies. The barriers are obtained by scanning potential energy surface for the movement of alkaline earth metal atoms and ions through the nanosheet. The size and morphology of defects in h-BN sheet significantly affect the energy barrier. h-BN sheet with V_N defect possess good Be/Be²⁺ selectivity. Permeation of Be atoms through V_BN-h-BN, V_B(2N)-h-BN and V_N(2B)-h-BN is a barrierless process. Mostly, the permeation barriers are reduced in the presence of water molecule for Be, Ca and Ca²⁺. The effect of water molecule is more pronounced on the permeation of Ca atom and ion through normal and defected h-BN sheet as compared to smaller alkaline earth metal atoms and ions. The study can be extended to investigate the separation capability of porous hexagonal boron nitride nanosheet for other metal atoms and ions.

Highlights

• Permeability of pristine and vacancy defected h-BN nanosheet is studied for alkaline earth metal atoms and ions.

• Increase in pore size and applied electric field decrease the permeation barriers for alkaline earth metal atoms and ions.

• V_N h-BN sheet possess good Be/Be²⁺ selectivity.

• Permeation of Be atoms through V_BN-h-BN, V_B(2N)-h-BN and V_N(2B)-h-BN is a barrierless process.

• Permeation barriers are reduced in the presence of water molecule for Be, Ca and Ca²⁺.

Communicated by Ramaswamy H. Sarma

Keywords:

• Vacancy defected h-BN membrane
• permeation barriers
• alkaline earth metals/ions
• selectivity ratios
• density functional theory

Acknowledgements

The authors acknowledge financial and technical support from Higher Education Commission of Pakistan and COMSATS University, Abbottabad Campus.