Assembling carbon quantum dots to a layered carbon for high-density supercapacitor electrodes

Area of Science:

• Materials Science
• Nanotechnology
• Electrochemistry

Background:

• Carbon quantum dots (CQDs) are promising nanomaterials with unique optical and electronic properties.
• Developing efficient methods for CQD assembly and their application in energy storage is an active research area.

Purpose of the Study:

• To investigate the self-assembly behavior of CQDs at the ice-water interface during freeze-drying.
• To fabricate and characterize free-standing CQD assemblies for supercapacitor applications.

Main Methods:

• CQDs were synthesized by KOH activation of C60, yielding approximately 15 wt.%.
• CQDs self-assembled into layered structures at the ice-water interface during freeze-drying.
• Annealed CQD assemblies were packaged into high-density electrodes (1.23 g cm⁻³).

Main Results:

• The self-assembled CQD layers exhibited an interlayer distance of ~0.366 nm, attributed to curved carbon rings.
• The synthesized CQDs had an average height of 1.14 nm and lateral size of 7.48 nm, showing high water solubility.
• Supercapacitor electrodes made from annealed CQD assemblies achieved a high volumetric capacitance of 157.4 F cm⁻³ and areal capacitance of 0.66 F cm⁻² in 6 M KOH.

Conclusions:

• Freeze-drying is an effective method for creating self-assembled, free-standing CQD structures.
• The unique layered assembly of CQDs enhances their performance in supercapacitors, offering high energy and power density.
• This work presents a scalable approach for fabricating advanced electrode materials for next-generation energy storage devices.