Ti₂NbC₂T_<i>x</i> MXene Nanosheets as an Ordered Double Transition Metal Electrode for High-Performance Supercapacitors

The increasing demand for advanced materials in energy storage underscores the importance of chemical diversity in nanomaterials. Ordered double transition metal (DTM) MXenes have emerged as promising atomically layered 2D materials. This study investigates the flexible Ti(2)NbC(2)T( x )MXene, synthesized from the ordered Ti2NbAlC2 MAX phase, as a supercapacitor electrode material. Electrochemical analyses revealed specific capacitances of 322 and 642 F g(-1) at a current density of 0.5 A g(-1) in Na2SO4 (Na) and H2SO4 (H) electrolytes, respectively. Ti2NbC2T x MXene exhibited exceptional cycling stability, retaining 95% capacitance in Na2SO4 and 100% in H2SO4 after 10,000 charge/discharge cycles. Furthermore, an asymmetric supercapacitor (ASC) was fabricated using Ti2NbC2T x MXene as the positive electrode and overcapacitive activated carbon as the negative electrode with PVA-Na and PVA-H gel electrolytes. The ASC achieved energy densities of 31.1 and 34.0 W h kg(-1 )for PVA-Na and PVA-H electrolytes, respectively. These results highlight the potential of Ti2NbC2T x MXene, with its unique ordered structure and double transition metal composition, for foundational research and applications in advanced energy storage technologies.