Improved pseudocapacitances of supercapacitors based on electrodes of nitrogen-doped Ti₃C₂T_x nanosheets with in-situ growth of carbon nanotubes

A facile strategy involving only liquid mixing, drying, and annealing processes has been designed to fabricate a new MXene-based material containing nitrogen-doped carbon nanotubes grown on the nitrogen-modified titanium carbides (NCMX). During the thermal treatment, the nitrogen doping is dually achieved in MXene nanosheets and carbon nanotubes while the in-situ growth of carbon nanotubes occurs. The NCMX electrode exhibits the well-designed structure with the promoted specific surface area and specific capacitance. More attractively, the resultant NCMX-4 material shows extraordinary improved electrochemical capacitances of 299.52 F g⁻¹ at the scan rate of 2 mV s⁻¹ in the 3 M H₂SO₄ electrolyte, which is remarkably more superior than those of the pure un-doped one (74.98 F g⁻¹). It delivers an excellent capacitance retention capability of 84.2% after 10,000 cycles. Our results highlight that the strategy of fabricating novel NCMX materials here can be readily applied to a large industrial scale for improving the pseudocapacitance of supercapacitors.