Gallic acid-derived carbon dots intercalated 3D porous Ti₃C₂T_x MXene for high-capacity supercapacitors

Ti3C2Tx Mxene shows good promise as an energy storage material. However, two-dimensional MXene materials are easily stacked, which negatively affects the energy density and limits the application of MXene-based supercapacitors. In this paper, a strategy for embedding carbon dots is proposed to address this issue. A three-dimensional structure is formed by cross-linking Ti3C2Tx MXene nanosheets with gallic acid (GA), and a subsequent carbonization process is then utilized to prepare a three-dimensional porous carbon dot intercalated Ti3C2Tx MXene material. The hydroxyl structures in GA are cross-linked with the hydroxyl structures on the surface of Ti3C2Tx under the action of Zn2+ to form a three-dimensional structure. The carbon dots formed by carbonizing the GA are embedded within the Ti3C2Tx nanosheets, which increases the Ti3C2Tx nanosheet layer spacing. The increase of layer spacing of Ti3C2Tx nanosheets is conducive to the diffusion and transport of electrolyte ions in Ti3C2Tx MXene. Consequently, at a scan rate of 2 mV s-1, a Ti3C2Tx@Celectrode achieves a high electrochemical gravimetric pecific capacitance (Cg) of 393.7 F g-1. At a higher scan rate of 200 mV s-1, 83.7% capacitance retention is obtained. Moreover, this electrode also shows 90.3% performance retention after 5000 cycles, demonstrating its good cycle stability. Finally, a symmetric supercapacitor was built using carbon cloth and Ti3C2Tx@C, and at a power density of 153.25Wkg-1, a superb energy density of 21.28Whkg-1is attained. This study offers a facile strategy for effectively preparing MXene electrodes with desirable electrochemical performance.