Carbon Dot-Regulated 2D MXene Films with High Volumetric Capacitance

The flexible and conductive carbon dots (CDs)/MXene films with zero-dimensional (0D)/two-dimensional (2D) dot-sheet motif architectures are successfully fabricated via the Coulombic interaction between negatively charged Ti3C2Tx MXene nanosheets and positively charged CDs synthesized from biomass by a green and economic one-pot hydrothermal process. The interlayer spacing coupled with the type and content of doped heteroatoms of the hybrid films can be regulated by the selected CDs with various particle sizes and heteroatoms. These CDs/MXene films with enlarged interlayer spacing and doped heteroatoms accelerate the ion diffusion and charge transfer. The optimized freestanding film electrode from pomelo juice with suitable layer spacing and profuse heteroatom doping indicates a high volumetric capacitance of 984.5 F cm–3 at a scan rate of 2 mV s–1, and a excellent volumetric energy density of 19.42 Wh L–1 is obtained in the corresponding assembled asymmetric supercapacitor. This study sheds light on a facile self-assembly route to fabricate multitudinous low cost and high-performance flexible MXene-based electrode.