Nitrogen-doped Ti3C2Tx MXene prepared by thermal decomposition of ammonium salts and its application in flexible quasi-solid-state supercapacitor

•It provides a green and effective strategy for rapid nitrogen doping into MXene.•Nitrogen doping can effectively increase the layer spacing of Ti3C2Tx MXene.•The as-prepared N-Ti3C2Tx shows enhanced pseudocapacitance of 449F g−1.•The N-Ti3C2Tx supercapacitor delivers an energy density of 12.78 Wh kg−1.•The strategy opens up a versatile approach for preparing N-MXene Materials.