Investigations on different two-dimensional materials as slit membranes for enhanced desalination

The use of two-dimensional (2D) materials as ultra-thin desalination membrane has garnered much interest in the scientific community. Various 2D materials membrane designs have been tested both numerically and experimentally. However, a detailed direct comparison between different 2D materials membrane is lacking. This study uses molecular dynamics (MD) to characterize and compare the desalination performance of graphene, borophene, molybdenum disulphide (MoS₂) and MXene slit membranes. It was found that monoelemental graphene and borophene have the best desalination performance. They achieve 100% monovalent salt rejection with permeability 25% higher than MoS₂ membranes and 87% higher than MXene membranes. Three factors are found to influence the desalination characteristics. Firstly, the hydrophobicity of the material which is found to increase salt rejection but reduce permeability. Second the material's inherent interaction parameters, and third the shape of the slits formed by atomic arrangement of the 2D material. Furthermore, although desalination performance varies across 2D materials membrane, all the membranes tested have permeability two orders of magnitude higher than current desalination membrane. All in all, this study highlights the varying characteristics of membrane made of different 2D materials and relate the material's properties with the resulting desalination performance.