Annealing Ti3C2Tz MXenes to control surface chemistry and friction

Although surface terminations (such as =O, -Cl, -F, -OH) on MXene nanosheets strongly influence their functional properties, synthesis of MXenes with desired types and distribution of those terminations is still challenging. Here, it is demonstrated that thermal annealing help to remove much of the terminal groups of molten salt-etched multi-layered (ML) Ti3C2Tz .In this study, the chloride terminations of molten salt etched ML-Ti3C2Tz were removed via thermal annealing at elevated temperatures under an inert (argon) atmosphere. This thermal annealing created some bare sites available for further functionalization of Ti3C2Tz . XRD, EDS, and XPS measurements confirm the removal of much of the terminal groups of ML-Ti3C2Tz . Here, the annealed ML�Ti3C2Tz were re-functionalized by -OH groups and 3-aminopropyl triethoxysilane (APTES), which was confirmed by FTIR. The -OH and APTES surface-modified ML-Ti3C2Tz are evaluated as a solid lubricant, exhibiting ~70.1% and 66.7% reduction in friction compared to steel substrate, respectively. This enhanced performance is attributed to the improved interaction or adhesion of functionalized ML-Ti3C2Tz with the substrate material. This approach allows for effective surface modification of MXenes and control of their functional properties