Interfacial Properties of Water on Hydrogenated and Fluorinated Graphene Surfaces: Parametrization of Nonbonded Interactions

The properties of water interfacing with functionalized two-dimensional (2D) materials play a crucial role in the design and development of high-performance nanofluidic devices. Developing nonbonding force field parameters that can be used in molecular dynamics simulations allows researchers to study and understand the interfacial properties at the molecular scale. Here, we use high-level ab initio simulations based on the random-phase approximation method to develop force field parameters for the interaction of water with hydrogenated/fluorinated graphene surfaces. By performing molecular dynamics simulations based on the force fields developed here, hydrogenated and fluorinated graphene surfaces are shown to be more hydrophobic compared to pristine graphene. Even though hydrogenated and fluorinated graphene surfaces having similar geometries, the fluorinated graphene has higher hydrophobicity due to its unique chemistry. The increase in the surface hydrophobicity leads to a decrease in the interfacial density and an increase in the slip length of water. Finally, we use first-principle simulations to show that a large decrease in the surface energy of the hydrogenated and the fluorinated graphene is the primary cause of their stronger hydrophobicity compared to pristine graphene.