Enhancing Pseudocapacitance in Ti3C2Tx with Its Own Hydroxyl-Rich Quantum Dots for Increased Redox Sites and Fast Ion Transport

Abstract

Although Ti₃C₂T_x MXene shows great promise as a pseudocapacitive material, 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 comparing with nanoflakes, hydroxyl-rich QDs exhibited higher specific pseudo-capacitance 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 high specific capacitance of 372.2 F/g at 10 mV/s (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 ). The incorporation of hydroxyl-rich QDs improved the stacking of nanoflake materials and alleviates mechanical stress during charge-discharge processes, thereby ensuring robust cycling stability. This study highlights the superior pseudocapacitance of hydroxyl-rich Ti₃C₂T_x QDs and significance of rational design of MXene-based hybrid materials for energy storage applications.