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

Abstract A step‐by‐step strategy is reported for improving capacitance of supercapacitor electrodes by synthesizing nitrogen‐doped 2D Ti 2 CT x induced by polymeric carbon nitride (p‐C 3 N 4 ), which simultaneously acts as a nitrogen source and intercalant. The NH 2 CN (cyanamide) can form p‐C 3 N 4 on the surface of Ti 2 CT x nanosheets by a condensation reaction at 500–700 °C. The p‐C 3 N 4 and Ti 2 CT x complexes are then heat‐treated to obtain nitrogen‐doped Ti 2 CT x nanosheets. The triazine‐based p‐C 3 N 4 decomposes above 700 °C; thus, the nitrogen species can be surely doped into the internal carbon layer and/or defect site of Ti 2 CT x nanosheets at 900 °C. The extended interlayer distance and c ‐lattice parameters ( c ‐LPs of 28.66 Å) of Ti 2 CT x prove that the p‐C 3 N 4 grown between layers delaminate the nanosheets of Ti 2 CT x during the doping process. Moreover, 15.48% nitrogen doping in Ti 2 CT x improves the electrochemical performance and energy storage ability. Due to the synergetic effect of delaminated structures and heteroatom compositions, N‐doped Ti 2 CT x shows excellent characteristics as an electrochemical capacitor electrode, such as perfectly rectangular cyclic voltammetry results (CVs, R 2 = 0.9999), high capacitance (327 F g −1 at 1 A g −1 , increased by ≈140% over pristine‐Ti 2 CT x ), and stable long cyclic performance (96.2% capacitance retention after 5000 cycles) at high current density (5 A g −1 ).