Multimodal-Based Computational Screening of the Capacitance of Two-Dimensional Metal Nitride MXenes via Synergistic Regulation of Chemical Compositions

MXenes are emerging as highly promising supercapacitor electrodes. However, the synergistic effects of their diverse surface terminations and transition metals on intrinsic and electrochemical capacitances remain elusive. Establishing a theoretical pipeline will be beneficial to efficiently understand the capacitive behavior and design high-performance materials. Here, we employ first-principles calculations in combination with the rigid band approximation (RBA) and constant potential free energy (CPFE) methods to perform a systematic investigation of the capacitive behavior via synergistic regulation of surface terminations and transition metals in M 3 N 2 T x (M = Ti, V, Zr, Nb, Mo, Hf, Ta, W; T x = O, S, Se, F, Cl, Br). The O-, S-, and Cl-terminated ones exhibit higher quantum capacitance performance than the others. A metal group-descending and period-ascending trend in capacitance is concluded. Moreover, the electrochemical capacitance is primarily governed by the electronegativities of the surface groups and changes in bond lengths. The combination of intrinsic and electrochemical capacitances achieves an optimal trade-off between computational efficiency and accuracy. Several candidates are predicted to possess both high capacitance and energy density, e.g., V 3 N 2 O 2 (167 F/g, 33.5 Wh/kg) and Ti 3 N 2 O 2 (163 F/g, 32.7 Wh/kg). Overall, we establish a full-spectrum evaluation paradigm that bridges electronic structure, interfacial phenomena, and capacitive performance, overcoming the limitations of conventional single-method studies and offering a robust theoretical foundation and predictive toolkit for the rational design of next-generation energy storage materials.