Fast water desalination by carbon-doped boron nitride monolayer: transport assisted by water clustering at pores

Abstract

The well-being of the ever-escalating world population hinges largely upon the adequacy of clean, fresh water. Desalination is one of the most promising approaches in such an endeavor. Using molecular dynamics simulations, we take a close look at nanoporous hexagonal boron nitride nanosheets as desalination membranes, and study how C dopants affect their performance. The calculations predict that the desalination performance of C-doped BN membranes compares favorably to that of MoS2 membranes: the water flux through the 0% (0CB–0CN), 25% (3CB–0CN), 75% (3CB–6CN), and 100% C terminated BN membrane (6CB–6CN) is 29.9, 47.5, 95.3, and 81.5 molecules ns−1 per pore, respectively, and there is a strong correlation between the water flux and the axial diffusion coefficient. Through our study of the effect of C content on the desalination performance, it is found that more clustering of water molecules at membrane pores due to a smaller hydration free energy and pore energy barrier assists water transport through the pores, and allows a greater water flux.