First-principles study for discovery of novel synthesizable 2D high-entropy transition metal carbides (MXenes)

Abstract

MXenes have been studied as promising 2D materials for various applications such as semiconductors, energy storage, supercapacitors, electromagnetic shielding, sensors, batteries, and adsorbents. In particular, 2D high-entropy MXenes are expected to improve the physical or chemical properties of MXenes through the combination of various transition metal compositions. However, it is challenging to experimentally investigate novel high-entropy MXene compositions owing to time and cost limitations. In the present study, using first-principles calculations, the synthesizability of high-entropy MXenes was determined by evaluating the thermodynamic stability and exfoliation possibility of high-entropy MAX phases, which are precursors of high-entropy MXenes. The high-entropy MXenes can be easily synthesized from few-layered and Al-based HE-MAX phases, which are composed of Ti, Nb, and Ta. Additionally, the thermodynamic stability and exfoliation possibility of high-entropy MAX phases are highly correlated with the lattice distortion factors (the standard deviation of bond length and differences in atomic radii) and the differences in the bond lengths of M–A and M–X, respectively. Out of 756 high-entropy MAX phase candidates, 146 high-entropy MXene compositions were estimated to be synthesizable. Furthermore, we successfully synthesized two novel high-entropy MXenes, (TiVNbTa)₂C and (TiVNbHfTa)₂C, which are expected to be highly synthesizable through our first-principles calculations.