Preparation of crumpled nitrogen-doped Ti3C2Tx

50 mL Ti3C2Tx colloidal solution (2 mg mL−1) was thoroughly mixed with 800 mg MF templates in a 100 mL distilled water. Upon centrifugation and freeze-drying, the product was annealed at 550 ℃ in an Ar ambient for 2 h to attain the crumpled nitrogen-doped MXene.