Structural insights into 2D materials for tribology

Owing to their excellent mechanical properties, two-dimensional (2D) materials show substantial promise for application in tribology. This has prompted a proliferation of novel 2D structures in numerous studies. However, ‌there is a lack of understanding regarding‌ the intrinsic relationship between their structure and lubrication performance, ‌which presents‌ a challenge to the systematic design of high-performance 2D ‌lubricating‌ materials. Therefore, this paper first classifies 2D lubricating materials into four categories based on their structural characteristics: inorganic, organic, carbon-based, and hybrid structures. Subsequently, it systematically reviews key research advances for each structural type within the field of tribology. This review encompasses fundamental studies on intrinsic lubrication ability—primarily investigated through microscopic experiments and theoretical simulations—as well as applied research exploring their use as lubricant additives (both oil- and water-based), lubricant coatings, and reinforcing phases in composite materials. Furthermore, the lubrication mechanisms of diverse 2D structures across various lubrication regimes have been systematically summarized, and strategies for enhancing performance via structural modification are also discussed. Finally, the current challenges and future research directions for 2D lubricating materials are critically analyzed.