Covalent Grafting of Dialkyl Dithiophosphate onto MXene Nanosheets for Synergistic Lubrication Enhancement

As an emerging two-dimensional (2D) material, MXene holds great promise as a lubricating additive. In this work, a dialkyl dithiophosphate (DDP)-functionalized MXene additive was synthesized by assembling epigallocatechin gallate (EGCG) and polyethylenimine (PEI) on Ti3C2Tx nanosheets, followed by the covalent grafting of DDP via a Michael addition reaction. The resulting DDP-MXene additive exhibits an enhanced tribological performance. With an addition of 0.5 wt %, the COF decreased to 0.10, compared with 0.32 for the base oil, and the wear volume decreased by 86%. In addition, the additive exhibits a good load-carrying capacity of up to 900 N. This improved lubrication performance arises from a synergistic lubrication mechanism: MXene nanosheets provide physical shearing, while a robust tribochemical film forms from DDP decomposition, providing improved antifriction and antiwear capabilities in severe service environments.