Functional Group Modulation in Carbon Quantum Dots for Accelerating Photocatalytic CO₂ Reduction

Area of Science:

• Materials Science
• Photocatalysis
• Carbon Quantum Dots

Background:

• Carbon quantum dots (CQDs) are emerging nanomaterials with tunable optical and electronic properties.
• Photocatalysis offers a sustainable route for CO2 reduction, but efficiency remains a challenge.
• Graphitic carbon nitride (CN) is a promising metal-free photocatalyst, yet its performance can be limited.

Purpose of the Study:

• To investigate the mechanism of enhanced photocatalytic performance in CQD-induced photocatalysts.
• To synthesize and characterize red luminescent CQDs (R-CQDs) and their composites with graphitic carbon nitride (CN).
• To evaluate the effect of surface functional groups on R-CQDs for CO2 reduction.

Main Methods:

• Microwave ultrafast synthesis was employed to prepare R-CQDs with varying surface functional groups.
• A facile coupling technique was used to synthesize R-CQD/CN composite photocatalysts.
• CO2 reduction experiments were conducted to assess photocatalytic activity and product selectivity.

Main Results:

• The R1-CQDs/CN composite exhibited a narrowed band gap and more negative conduction band potential, reducing electron-hole recombination.
• Enhanced light absorption, increased carrier concentration, and improved deoxygenation ability were observed.
• R1-CQDs/CN demonstrated a CO production rate of 77 μmol g-1 in 4 h, 5.26 times higher than pure CN.
• Superior photocatalytic performance was attributed to a strong internal electric field and high Lewis acidity/alkalinity.

Conclusions:

• The R1-CQDs/CN composite shows remarkable photocatalytic activity and stability for CO2 reduction.
• Surface functional groups on R-CQDs play a crucial role in enhancing photocatalytic efficiency.
• This study presents a promising strategy for developing efficient CQD-based photocatalysts for energy and environmental applications.