Macro-Superlubricity Induced by Synergistic Effect of Molybdenum Carbide/Molybdenum Disulfide Heterojunction and...

Macroscopic solid-liquid synergistic superlubricity based on two-dimensional (2D) materials and liquid molecules integrates the low interlayer shear strength of 2D materials with advantages of liquid superlubricity, significantly reducing friction and wear in industrial applications. However, the low load-bearing capacity of single 2D material and the unclear synergistic superlubricity mechanism severely constrain the design of long-lasting superlubricity systems. Herein, through innovatively introducing van der Waals interaction-induced molybdenum carbide/molybdenum disulfide (Mo₂CT_x/MoS₂) heterojunction as additives in ethylene glycol (EG), this Mo₂CT_x/MoS₂-EG superlubricity system exhibits an ultralow friction coefficient of 0.0044, an extremely low wear rate of 8.17 × 10^-10 mm³•N^-1•m^-1, and an ultralong lubrication life of 432 000 cycles (equal to 2160 m). Meanwhile, the maximum average contact pressure reaches 711.9 MPa. The in-situ formed special tribofilms enriched with heterojunction and homojunction nanosheets effectively reduce the shear strength under boundary lubrication. Notably, the ultralow shear strength at the Mo₂C-O/EG solid-liquid interface and the unique pressure-responsive lubrication properties of EG molecules which leads to the formation of short-range-ordered structures are also crucial for achieving superlubricity. This study provides a new perspective for designing novel solid-liquid synergistic superlubricity systems by utilizing heterojunction nanomaterial and has great potential for application in industrial lubrication.