Facile synthesis of nitrogen and oxygen co-doped C@Ti3C2 MXene for high performance symmetric supercapacitors

Abstract Ti3C2 is considered as a promising electrode material for supercapacitors due to its excellent electronic conductivity and chemical stability. However, the relatively low specific capacitance of Ti3C2 hinders its further development in supercapacitors. Herein, the nitrogen and oxygen co-doped C@Ti3C2 composites have been synthesized through an in-situ polymerization method under annealing atmospheres of Ar and the mixture of Ar and NH3. The concentrations of doped N and O vary with the reaction atmosphere, thus influencing the electrochemical performance of the electrode material. Due to the synergistic effect of the additional pseudocapacitance provided by the abundant O- and N- functional groups in the carbon and the excellent electronic conductivity of Ti3C2, N, O co-doped C@Ti3C2 composite with N concentration of 9.5% exhibits a specific capacitance of 250.6 F g−1 at 1 A g−1, remaining 94% retention after 5000 cycles. Furthermore, the N, O co-doped C@Ti3C2 composite-based symmetric supercapacitor shows an energy density as high as 10.8 Wh kg−1 at a power density of 600 W kg−1 with excellent cycling stability. This study demonstrates that the performance of MXene-based supercapacitors can be greatly enhanced by designing and modifying with rich pseudocapacitive materials.