A First-Principles Study of Impurity-Enhanced Adhesion and Lubricity of Graphene on Iron Oxide Surface

Graphene is well-known as one of the best solid lubricants for its superlubricity and high mechanical strength. Weak adhesion leading to low interfacial compatibility is a significant challenge of the use of graphene in harsh conditions. In this work, guided by density functional theory (DFT) calculations, we propose a method to improve graphene compatibility on Fe2O3 by substituting B, P, S, and Si to some carbon sites. The results of binding energy and potential energy surface (PES) show that the selection of suitable elements with a reasonable concentration not only greatly improves graphene adhesion but also provides a better frictional property than that with pure graphene. The doped-graphene chemically binds on the surface through the formation of covalent bonds between the dopant atoms and iron of the surface. Bader charge analyses suggest that the doping of B and P causes a severe charge alteration at the nearest carbon C1, and a strong repulsion at the C1-C1 stacking sites at the sliding interface, leading to a reduction in corrugation energies and thus nanoscale friction. Furthermore, first-principles molecular dynamics (FPMD) simulations at high temperature reveal that thanks to well-adhered behavior, the doped-graphene shows a significant reduction in the structural deformation, especially the out-of-plane component, which is essential to maintain graphene's ultralow friction regime under harsh conditions. The current results shed light on further improved graphene performance without affecting its superlubricity.