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 Ti2CTx 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 Ti(2)CTx nanosheets by a condensation reaction at 500-700 degrees C. The p-C3N4 and Ti(2)CTx complexes are then heat-treated to obtain nitrogen-doped Ti2CTx nanosheets. The triazine-based p-C3N4 decomposes above 700 degrees C; thus, the nitrogen species can be surely doped into the internal carbon layer and/or defect site of Ti2CTx nanosheets at 900 degrees C. The extended interlayer distance and c-lattice parameters (c-LPs of 28.66 angstrom) of Ti2CTx prove that the p-C3N4 grown between layers delaminate the nanosheets of Ti2CTx during the doping process. Moreover, 15.48% nitrogen doping in Ti2CTx improves the electrochemical performance and energy storage ability. Due to the synergetic effect of delaminated structures and heteroatom compositions, N-doped Ti2CTx 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 approximate to 140% over pristine-Ti2CTx), and stable long cyclic performance (96.2% capacitance retention after 5000 cycles) at high current density (5 A g(-1)).