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

Ti 3 C 2 T x 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 Ti 3 C 2 T x MXene nanosheets with gallic acid (GA), and a subsequent carbonization process is then utilized to prepare a three-dimensional porous carbon dot intercalated Ti 3 C 2 T x MXene material. The hydroxyl structures in GA are cross-linked with the hydroxyl structures on the surface of Ti 3 C 2 T x under the action of Zn 2+ to form a three-dimensional structure. The carbon dots formed by carbonizing the GA are embedded within the Ti 3 C 2 T x nanosheets, which increases the Ti 3 C 2 T x nanosheet layer spacing. The increase of layer spacing of Ti 3 C 2 T x nanosheets is conducive to the diffusion and transport of electrolyte ions in Ti 3 C 2 T x MXene. Consequently, at a scan rate of 2 mV s -1 , a Ti 3 C 2 T x @Celectrode achieves a high electrochemical gravimetric pecific capacitance (C g ) 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 Ti 3 C 2 T x @C, and at a power density of 153.25Wkg -1 , a superb energy density of 21.28Whkg -1 is attained. This study offers a facile strategy for effectively preparing MXene electrodes with desirable electrochemical performance.