Modeling phosphorene and MoS2 interacting with iron: lubricating effects compared to graphene

Phosphorene, a single layer of black phosphorus, is attracting interest for several applications, among which tribology. Here, we investigate its possible use as a solid lubricant for iron-based materials by comparing its friction-reduction properties with MoS2 and graphene. Through first-principle calculations, we predict that phosphorene adheres more strongly to the native iron surface than the other considered 2D materials. The higher adhesion suggests that a stable and durable coverage of reactive surface regions can be obtained with phosphorene. Furthermore, our simulation uncovers the peculiar behavior of phosphorene to exfoliate into two atomic-thin layers upon interface intercalation. This capability makes phosphorene reduce the nano-asperity adhesion very efficiently thanks to the simultaneous passivation of the surface and countersurface. These results suggest that better performances could be obtained by phosphorene than other solid lubricants at low concentrations.