Two-dimensional molybdenum carbide (MXene) as an efficient nanoadditive for achieving superlubricity under ultrahigh pressure

Abstract In this study, a robust macroscale liquid superlubricity with a coefficient of friction of 0.004 was achieved by introducing molybdenum carbide (Mo 2 CT x ) MXene nanoparticles as lubricating additives in a lithium hexafluorophosphate-based ionic liquid at Si 3 N 4 —sapphire interfaces. The maximal contact pressure in the superlubricity state could reach 1.42 GPa, which far exceeds the limit of the superlubricity regime in previous studies. The results indicate that a composite tribofilm (mainly containing molybdenum oxide and phosphorus oxide) that formed at the interface by a tribochemical reaction contributed to the excellent antiwear performance. Furthermore, the extremely low shear strength of the tribofilm and the interlayers of Mo 2 CT x MXene contributed to the superlubricity. This work demonstrates the promising potential of Mo 2 CT x MXene in improving superlubricity properties, which could accelerate the application of superlubricity in mechanical systems.