A nitrogenous pre-intercalation strategy for the synthesis of nitrogen-doped Ti3C2Tx MXene with enhanced electrochemical capacitance

Tremendous efforts have been dedicated towards high-performance energy storage devices though material innovation, nanoscale structural design and hybrid fabrication approaches. A crucial technique to tune the properties of nanomaterials, such as MXene, is through introducing defects or heteroatom dopants. To improve the level of nitrogen dopant, a two-step pre-intercalation-annealing strategy is developed herein, using ammonium citrate (AC) as an all-in-one intercalant, antioxidant and nitrogen source, followed by annealing in an ammonia atmosphere. It is shown that the doping efficiency of nitrogen-doped Ti3C2Tx MXene (N-MXene) increased from 3.5% to 6.3%, compared with MXene annealed in ammonia without pre-intercalation. This high doping level induces significantly enhanced electrochemical capacitance (475 F g(-1) at 5 mV s(-1)) compared with pristine MXene (321 F g(-1)), and greatly improved performance at high current density (248 F g(-1) at 1 V s(-1)). Modelling was performed to elucidate the N-doping process of MXene and to understand the mechanism enhancing the electrochemical capacitance, which indicates that the pre-intercalation strategy promotes N-doping as surface functionalization, as well as in the MXene lattice. The pre-intercalation strategy demonstrates a new and facile pathway for functionalizing Ti3C2Tx MXene which will facilitate use in applications such as in high performance supercapacitors.

Automated summary

This study successfully increased the doping efficiency of nitrogen-doped Ti3C2Tx MXene through a pre-intercalation strategy, significantly enhancing its electrochemical capacitance performance, providing a new pathway for the functionalization of Ti3C2Tx MXene.