Origin of superlubricity promoted by black phosphorus dotted with gold nanoparticles

Black phosphorus (BP) has attracted considerable attention due to the outstanding mechanical and structural properties. However, the nanoscale frictional properties and atomic-scale mechanism of BP dotted with nanoparticles are still not well understood. Herein, gold nanoparticles (nano-Au) dotted on black phosphorus (Au/BP) are applied as nanoadditives for PAO6 oil to produce macroscale superlubricity at the Si₃N₄/MoN interface. Experiments and molecular dynamics simulation reveal that nano-Au not only enhances adsorption of oil molecules on Au/BP via strong hydrogen bonding, but also leads to incommensurate interlayer stacking of BP responsible for the superlubricity. The findings provide fundamental knowledge about the nanoscale frictional behavior as well as superlubricity mechanisms and also reveal a novel concept to design nanoadditives with superlubricity.