Effects of Intercalation on ML-Ti₃C₂T_<i>z</i> MXene Properties and Friction Performance

Intercalation in two-dimensional (2D) materials can modify their physical, chemical, and electronic properties. This modification enables the tailoring of 2D material characteristics, enhancing their performance and expanding their applications in various fields. The friction performance of 2D materials such as MoS₂ and graphite has a strong dependence on their interlayer spacing, and they exhibit an increase in <i>d</i>-spacing associated with a reduction in friction performance. The ability to control the interlayer spacing of Ti₃C₂T_<i>z</i> MXene has proven beneficial for energy storage applications such as batteries and supercapacitors, but no one has utilized this control of interlayer spacing for lubrication. In this study, we demonstrate that interlayer spacing of multilayer (ML) Ti₃C₂T_<i>z</i> MXene can be controlled through chemical intercalation and its direct effects on the electrical conductivity and friction performance. We observed a notable decrease in electrical conductivity in vacuum-filtered ML-Ti₃C₂T_<i>z</i> MXene films, which was attributed to an increased internal resistance resulting from the expansion of the interlayer gap. We also found a significant reduction in the coefficient of friction for ML-Ti₃C₂T_<i>z</i> MXene with an increased <i>d</i>-spacing. This reduction is attributed to a weakened attraction of individual ML-Ti₃C₂T_<i>z</i> MXene layers (intercalated). Under a tangential force, it becomes easier to slide within the larger interlayer gap with weakened van der Waals forces. This work provides insights into the tunability of MXene properties through interlayer spacing, offering potential applications requiring materials with specific electrical and friction characteristics.