Structural Stability and Electronic Transport Properties of Nb₂C‐MXenes under High Pressure

Abstract The extraordinary electronic properties of MXenes are closely associated with their surface terminations and external strain. Herein, by applying pressure, the structural and electronic properties of Nb 2 C‐MXenes with two different terminations F (Nb 2 CF x ) and Cl (Nb 2 CCl x ) are reported. Through high‐pressure X‐ray diffraction and scanning electron microscopy, it is observed that Nb 2 CF x loses its layered structure and becomes disordered above 20 GPa, while Nb 2 CCl x remains as layered structures up to 42.5 GPa. Surprisingly, the stable Nb 2 CCl x shows the axial compression coefficients with 1174.5 ± 39.2 GPa along the c axis and 1234.8 ± 25.8 GPa along the a axis, even larger than that of its precursor Nb 2 AlC MAX phase. It is also found that the resistance of Nb 2 CF x exhibits a drop of two orders of magnitude from the ambient pressure. Accompanied by a slight increment of the superconducting transition temperature, the superconductivity of Nb 2 CCl x survives up to 50.5 GPa. The results uncover the effects of surface terminations on structural stability and electronic properties of Nb 2 C‐MXenes under high pressure.