High-throughput screening of medium-entropy MXene-based supercapacitors

MXenes, a class of 2D transition metal nitrides and carbides, continues to attract attention as a promising material for supercapacitor applications. This study presents a high-throughput screening of both single-metal and medium-entropy MXenes using Density Functional Theory (DFT), in particular, the M2C and M3C2 structures, comprising of such M's as Ti, V, Nb, Cr, Ta, and Mo. The systematically evaluated quantum capacitance of these materials reveals that Nb3C2 exhibits the highest capacitance of 5983.8 μF/cm 2 amongst single-metal MXenes, while (TiVCrTa)0.75C2 and (TiCrNbTa)0.5C lead amongst medium-entropy variants with capacitances of 4706.3 and 3238.8 μF/cm 2 , respectively. The results highlight a synergistic enhancement in quantum capacitance due to multi-metal configurations of which the linear combinations of single-metal counterparts may not predict. Moreover, the ab initio molecular dynamics (AIMD) simulations further demonstrate the dynamic behaviour of quantum capacitance and the role of phonon-induced fluctuations, leading to the quantum coherence of 3.5 femtoseconds. This work paves down a theoretical foundation for guiding experimental efforts toward the design of next-generation MXene-based supercapacitors. • High-throughput DFT calculations is done on single-metal & medium-entropy MXenes of M₂C and M₃C₂. • Identified Nb₃C₂ as the top-performing single-metal MXene with a quantum capacitance of 5983.8 μF/cm 2 . • Discovered (TiVCrTa)₀.₇₅C₂ as the best medium-entropy MXene with a capacitance of 4706.3 μF/cm 2 . • AIMD simulations revealed that quantum capacitance fluctuates dynamically over time. • DOS analysis showed that d-orbitals of transition metals has critical roles in quantum capacitance.