Ultrasound assisted preparation of Ti₃C₂Tx MXene/carbon nanotube/MnO₂ ternary composite with superior capacitive...

MXenes have shown potential as energy storage materials. However, their practical application is limited by challenges in preparing monolayer or few-layer structures, including low yield and a tendency to restack. In this study, a three-dimensional porous composite with a hierarchically porous architecture was constructed by anchoring MnO₂ nanosheets onto an MXene/CNT framework via ultrasound assisted approach. The Ti₃C₂Tx MXene/CNT/MnO₂ composite demonstrated enhanced electrochemical performance with a specific capacitance of 271F/g in a 1 M H₂SO₄ electrolyte. After 10,000 cycles of tests, more than 99% of the capacitance is retained for the as-prepared ternary composite, which is significantly higher than that of the untreated Ti₃C₂Tx MXene. XPS characterization revealed that the Ti 2p_3/2 peak in the composite shifted markedly from 454.0 eV for pristine MXene to 455.9 eV, indicating an elevated oxidation state of Ti. This increase in binding energy is primarily attributed to the ultrasound-promoted enrichment of surface oxygen-containing functional groups, which collectively modified the coordination environment of Ti. Furthermore, the combination of the highly conductive carbon nanotube network and the pseudocapacitive MnO₂ significantly reduces the ion diffusion length, leading to significantly improved rate capability.