Regulated Layer Spacing and Functional Surface Group of Mxene Film by Hexamethylenetetramine for High-Performance Supercapacitors

The intercalation of spacer is a commonly used method for suppressing re-stacking of MXene nanosheets. However, the intrinsically inactive property of spacer injures the capacitance performance of MXene in acid electrolyte. Here, hexamethylenetetramine (HMT) molecules are used as the intercalation agents to inhibit the re-stacking of MXene nanosheets and regulate their electronic structure by the partial replacement of the surface functional groups (-F, -O and -OH) with N elements via the carbonization temperature at 300 o C. The as-prepared N-doped MXene film exhibits the appropriate layer spacing, excellent flexibility and high electrical conductivity, which could be used directly as supercapacitor electrode materials. It delivers the excellent rate performance with a specific capacitance of 193 F g -1 at 2000 mV s -1 . In addition, the assembled asymmetric supercapacitor with N-doped graphene aerogel, delivers a high energy density of 26.22 W h kg -1 at a power density of 899 W kg -1 , and the capacitance retention of 92.1% after 25,000 discharging/charging cycles, indicating the excellent application prospect