Phosphorene, a single layer of black phosphorus, is attracting interest in the scientific community for its semiconducting properties. However, phosphorene also possesses a great potential for tribological applications due to its layered structure and for the capability of P-based lubricant additives to reduce friction and adhesion in steel-steel contacts. In spite of these promising characteristics, the investigations of the lubricating properties of phosphorene are still at their infancies. To fill this gap we performed a comprehensive analysis of the tribological properties of phosphorene based on first principles calculations. Firstly, we estimated the interlayer work of separation and shear strength for the bilayer system. A structural superlubricity is identified for a perpendicular orientation of the layers. [1]

As a second step in our analysis, we investigated the capability of phosphorene to lubricate the iron interfaces, in comparison with well-established iron coatings. We demonstrated the firm adhesion of phosphorene with the iron surface through DFT simulations, which potentially indicates a stable and durable lubricating effect. Furthermore, our simulations show that a single phosphorene flake can reduce the adhesion energy of two mating iron surfaces more efficiently than any other 2D material, such as MoS2 and graphene [2, 3]. This efficient lubrication is driven by the peculiar structure of phosphorene that can split in two atomic planes upon intercalation at the metallic surface.

The presented results are part of the "Advancing Solid Interface and Lubricants by First Principles Material Design (SLIDE)" project that has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Grant agreement No. 865633).

References

[1] G. Losi, P. Restuccia, M.C. Righi; Superlubricity in phosphorene identified by means of ab initio calculations, 2D Mater. 7, 025033 (2020)

[2] G. Losi, M. Cutini, P. Restuccia, M. C. Righi; Intra-layer exfoliation of phosphorene enhances its lubricating properties on iron, a comparison with MoS2 and graphene, submitted
[3] P. Restuccia and M. C. Righi; Tribochemistry of graphene on iron and its possible role in lubrication of steel, Carbon 106, 118–124 (2016)