Termination-dependent interfacial interactions of ionic-liquid-modified Ti3C2Tx for boundary lubrication

An interfacial energetic hierarchy governs IL-Ti 3 C 2 T x boundary lubrication. • Termination-driven energetic inversion decouples anchoring and retention. • Retention is governed by Ti 3 C 2 T x -metal coupling rather than cation anchoring. • IL-Ti 3 C 2 T x reduces wear by 61% at 0.05wt.% via a stable tribofilm. The effectiveness of two-dimensional additives in boundary lubrication is often limited by poor dispersion stability and unstable low-shear interfaces in polar lubricants. Here, we report an ionic liquid (IL)-enabled interfacial-engineering strategy that couples surface anchoring with shear regulation at Ti 3 C 2 T x MXene interfaces. Density functional theory (DFT) calculations suggest that the imidazolium cation acts as the primary anchoring motif, showing strong, termination-sensitive binding to Ti 3 C 2 T x surface terminations, while the alkyl chain extends toward the counterface and may provide a molecular basis for an organic shear-accommodating overlayer. First-principles calculations further indicate a termination-dependent interfacial interaction trend, in which the calculated stability of the composite layer on steel is more closely associated with Ti 3 C 2 T x -Fe electronic coupling than with cation-Ti 3 C 2 T x anchoring. This trend provides a possible mechanistic basis for reconciling interfacial persistence with low shear resistance. Accordingly, IL-modified Ti 3 C 2 T x reduces wear by up to 61% at an ultralow concentration of 0.05wt.%. Tribochemical and cross-sectional TEM analyses support the formation of an 8.5 nm continuous composite tribofilm enriched with IL- and Ti 3 C 2 T x -derived species, consistent with reduced direct steel exposure during sliding. These findings offer design concepts for two-dimensional additives in polar lubricants. Download: Download high-res image (244KB) Download: Download full-size image