A Strategy for Synthesis of Carbon Nitride Induced Chemically Doped 2D MXene for High‐Performance Supercapacitor Electrodes

A step‐by‐step strategy is reported for improving capacitance of supercapacitor electrodes by synthesizing nitrogen‐doped 2D Ti₂CT_x induced by polymeric carbon nitride (p‐C₃N₄), which simultaneously acts as a nitrogen source and intercalant. The NH₂CN (cyanamide) can form p‐C₃N₄ on the surface of Ti₂CT_x nanosheets by a condensation reaction at 500–700 °C. The p‐C₃N₄ and Ti₂CT_x complexes are then heat‐treated to obtain nitrogen‐doped Ti₂CT_x nanosheets. The triazine‐based p‐C₃N₄ decomposes above 700 °C; thus, the nitrogen species can be surely doped into the internal carbon layer and/or defect site of Ti₂CT_x nanosheets at 900 °C. The extended interlayer distance and c‐lattice parameters (c‐LPs of 28.66 Å) of Ti₂CT_x prove that the p‐C₃N₄ grown between layers delaminate the nanosheets of Ti₂CT_x during the doping process. Moreover, 15.48% nitrogen doping in Ti₂CT_x improves the electrochemical performance and energy storage ability. Due to the synergetic effect of delaminated structures and heteroatom compositions, N‐doped Ti₂CT_x shows excellent characteristics as an electrochemical capacitor electrode, such as perfectly rectangular cyclic voltammetry results (CVs, R² = 0.9999), high capacitance (327 F g^?1 at 1 A g^?1, increased by ≈140% over pristine‐Ti₂CT_x), and stable long cyclic performance (96.2% capacitance retention after 5000 cycles) at high current density (5 A g^?1).