Defect Engineering of MXenes at Elevated Temperatures

The chemically diverse family of 2D MXenes have been widely adopted in areas such as energy storage, conversion, and electronics. From the ceramic perspective, MXenes uniquely enable the atomic control of its structure at the ~1 nm scale. In this presentation, we demonstrate the defect engineering of Mo₂TiC₂T<i>_x</i>, Ti₃C₂T<i>_x</i>, Mo₂Ti₂C₃T<i>_x</i>, and Nb₂CT<i>_x</i> MXenes at elevated temperatures using alkali cations. We demonstrate the improved phase stability of MXenes and control of formed carbide phases using <i>in situ</i> x-ray diffraction and scanning transmission electron microscopy techniques. Further, we present evidence for the role of partial occupation of alkali cations in defective sites in MXenes using computational methods paired with <i>in </i>and <i>ex </i>situ methods. Overall, this cation-based engineering of defects in 2D MXenes demonstrates the potential for improving their stability and further develops the tools for researchers to apply MXenes as a diverse and tunable family of nanoceramics for high temperature applications.