Comparison of water desalination performance of porous graphene and MoS2 nanosheets

Abstract

Following graphene and its derivatives, molybdenum disulfide (MoS₂) has become a research hotspot in two-dimensional materials. Both graphene and MoS₂ exhibit great potential in water treatment. A variety of nanoporous graphene or MoS₂ membranes have been designed for water desalination. In this work, we compared the water flux and ion rejection of MoS₂ and graphene nanopores, using molecular dynamics simulations. The simulation results demonstrate that monolayer nanopores have higher water fluxes than bilayer nanopores with lower ion rejection rates. MoS₂ nanopores perform better than graphene in terms of water permeability. Exploration of the underlying mechanism indicates that the water molecules in the MoS₂ pores have faster velocity and higher mass density than those in the graphene pores, due to the outer hydrophobic and inner hydrophilic edges of MoS₂ pores. In addition, increasing the polarity of the pore edge causes a decrease in water flux while enhancement of ion rejection. Our findings may provide theoretical guidance for the design of MoS₂ membranes in water purification.