Enhancing the pseudocapacitance of Ti ₃ C ₂ T _x with its own hydroxyl-rich quantum dots for increased redox sites and fast ion transport

Although Ti₃C₂T_x MXene shows great promise as a pseudocapacitive material, its limited edge sites and slow interlayer ion transport restrict its electrochemical performance. In this paper, hydroxyl-rich Ti₃C₂T_x quantum dots (QDs) were synthesized by intercalation with tetramethylammonium hydroxide (TMAOH) and hydrothermal cutting. It was found that compared with nanoflakes, hydroxyl-rich QDs exhibited higher specific pseudocapacitance and rapid redox kinetics, which can be attributed to their abundant surface redox-active sites and efficient ion transport facilitated by hydrogen-bond networks. The incorporation of 20 wt% hydroxyl-rich QDs into nanoflakes exhibits not only a high specific capacitance of 372.2 F g^-1 at 10 mV s^-1 (20% higher than that of Ti₃C₂T_x nanoflakes alone), but also significantly enhanced cycling stability (100% capacitance retention after 10 000 cycles at a current density of 10 A g^-1). The incorporation of hydroxyl-rich QDs improved the stacking of nanoflake materials and alleviated mechanical stress during charge-discharge processes, thereby ensuring robust cycling stability. This study highlights the superior pseudo-capacitance of hydroxyl-rich Ti₃C₂T_x QDs and the significance of rational design of MXene-based hybrid materials for energy storage applications.