Electrostatic self-assembled ZnO quantum dots/MXene composite film for high-performance supercapacitor

MXene has gained prominence as a prospective electrode material for supercapacitors owing to its unique layered architecture, high electrical conductivity and intrinsic hydrophilicity. However, the intrinsic tendency for severe interlayer restacking in MXene markedly restricts the exposure of electrochemically active surface sites. In this work, we prepare a ZnO quantum dots/MXene composite film electrode with a 0D-2D structure and evaluate its electrochemical performance in neutral aqueous electrolyte (1.5 M Na 2 SO 4 ). The synergistic interfacial interaction between ZnO QDs and Ti 3 C 2 T x nanosheets facilitates enhanced specific surface area and the optimized utilization efficienc of electroactive site. Notably, even with an average size of 16.3 nm, the incorporated ZnO nanoparticles with a relatively high degree of dispersion still contribute significantly to the enhanced performance of the Ti 3 C 2 T x electrode. This structural configuration endows the ZnO QDs/Ti 3 C 2 T x composite with superior energy storage capability (305 F g −1 at 0.5 A g −1 ) and remarkable rate performance, outperforming pristine Ti 3 C 2 T x electrodes (125.87 F g −1 ). After 5000 charge-discharge cycles at a current density of 10 A g −1 , the capacitance retention rate is 96.79 %, showing excellent cycle stability. The quasi-solid-state symmetric supercapacitor based on ZnO QDs/Ti 3 C 2 T x exhibits a high energy density of 8.2 Wh kg −1 at a power density of 349 W kg −1 . Notably, even after 5000 cycles, the SSCs exhibit a capacitance retention rate of 93.44 %, demonstrating outstanding cycling stability.