Charge Exchange and Transfer between Water and van der Waals Monolayers Under Tensile Strains

Charge exchange and transfer between water and low-dimensional materials are critical for water-related nanogenerators to harvest electricity from water. By first-principles calculations and molecular dynamics simulations, the interface interaction and charge transfer between ion-containing or pure water and two-dimensional (2D) van der Waals monolayers including transition metal dichalcogenides, hexagonal boron nitride, and graphene have been systematically investigated. Applying uniaxial tensile strain or the introduction of defects on 2D monolayers could significantly enhance the interface interaction and charge transfer from 2D monolayers to water molecules, as the tensile strain or defect weakens the bonds of 2D monolayers and changes the hydrogen bond networks in the interfacial water layer. In contrast, the presence of ions in water suppresses the charge transfer from 2D monolayers to water molecules and reduces interfacial adhesion because of the formation of hydrated ions and stronger charge exchange between ions and water molecules. These results reveal the role of strain, defect, and ion in dominating the charge exchange and transfer between water and 2D monolayers.