Unveiling the Tribological Potential of Borophene Nanosheets as a High-Performance Lubricant Additive

Reducing friction and wear in industrial systems is crucial for enhancing energy efficiency, machinery longevity, and environmental sustainability. For the first time, this study explores borophene, a two-dimensional (2D) nanomaterial, as an additive in castor oil for lubrication applications. Borophene’s electron-deficient surface and unique 2D morphology facilitate strong interactions with castor oil’s ricinoleic acid, promoting stable dispersion without surface functionalization. A minimal loading of 0.1 wt % borophene significantly improves tribological performance, decreasing the average coefficient of friction from 0.059 (pure castor oil) to 0.034, corresponding to a 42% reduction. Surface roughness of the steel counterface also decreases markedly ( R a from 0.826 to 0.326 μm; R q from 1.01 to 0.405 μm), indicating a smoother, more protective tribofilm. Detailed analyses using XPS and TOF-SIMS reveal that the tribofilm is a hybrid structure comprising iron oxides (FeO, Fe 2 O 3, Fe 3 O 4 ), hydroxides (FeOOH), carbonaceous residues from castor oil, and boron-containing species (BO 2 –, FeBO + ), which together reduce shear stress, enhance load-bearing capability, and resist wear. The synergistic combination of borophene’s chemical reactivity and facile interlayer shearing enables the formation of a durable, low-shear tribofilm, transforming castor oil into a high-performance biolubricant. These findings establish borophene as a effective additive for energy-efficient lubrication