Regulating d-Band Center of Ti₂ C MXene Via Nb Alloying for Stable and High-Efficient Supercapacitive Performances

Ti₂ C MXene with the lowest formula weight is expected to gain superior advantages in gravimetric capacitances over other heavier MXenes. Nevertheless, its poor chemical and electrochemical stability is the most fatal drawback and seriously hinders its practical applications. Herein, an alloy engineering strategy at the transition metal-sites of Ti₂ C MXene is proposed. Theoretical calculations reveal that the electronic redistribution of the solid-solution TiNbC MXene improves the electronic conductivity, induces the upward d-band center, tailors the surface functional groups, and increases the electron loss impedance, resulting in its excellent capacitive performance and high chemical stability. The as-prepared flexible TiNbC film delivers specific capacitance up to 381 F g^-1 at a scan rate of 2 mV s^-1 and excellent electrochemical stability without capacitance loss after 10000 charge/discharging cycles. This work provides a universal approach to develop high-performance and chemically stable MXene electrodes.