Enhancing the quantum yield and electrochemical properties of carbon quantum dots via optimized hydrothermal treatment using cellulose nanocrystals as precursors.

Carbon quantum dots (CQDs) are receiving increasing attention due to their tunable redox activity, abundant surface functional groups, and excellent aqueous dispersion. However, their low quantum yield remains a significant impediment to their synthesis and practical application. In the present work, cellulose nanocrystals (CNCs) were utilized as precursors for the optimized hydrothermal synthesis of CQDs. Subsequently, the synthesized CQDs were electrodeposited onto a carbon-coated surface. The influence of hydrothermal temperature and time on the quantum yield and electrochemical properties of CQDs was systematically explored. The successfully synthesized CQDs exhibited an average particle size of approximately 5 nm. The quantum yield was enhanced from 14.35 % to 23.7 % as the hydrothermal temperature increased from 180 °C to 230 °C. Additionally, the electrochemical properties of the composite films were investigated. Electrochemical assessments demonstrated an increase in specific capacitance from 60.4 mF·cm to 65.2 mF·cm with an elevation in temperature from 180 °C to 210 °C. Remarkably, the CQDs displayed higher energy density (8.819 mWh·cm) and power density (1800 mW·cm) at 210 °C for 8 h. This work offers a scalable approach for the efficient production of high-performance CQDs, showcasing their substantial potential for supercapacitor applications.