NH₃-Guided Low-Temperature Nanostructural Refinement Boosts Visible-Light-Driven H₂O₂ Synthesis in Ionic Carbon...

Area of Science:

• Materials Science
• Photocatalysis
• Green Chemistry

Background:

• Solar-driven production of hydrogen peroxide (H2O2) is a sustainable alternative to traditional methods.
• Ionic carbon nitride frameworks, like potassium poly(heptazine imide) (KPHI), show promise for photocatalysis.
• Optimizing KPHI's nanostructure and defect chemistry is crucial for enhancing its efficiency.

Purpose of the Study:

• To develop a nanostructural engineering strategy for KPHI to improve its solar-driven H2O2 production.
• To tailor KPHI's morphology and introduce cyano (-C≡N) defects for enhanced photocatalytic activity.
• To investigate the structure-activity relationship in ionic carbon nitrides for controlled synthesis.

Main Methods:

• Incorporation of NH4Cl into a molten KCl/LiCl eutectic medium to fragment KPHI crystals and introduce cyano defects.
• Synthesis of a low-temperature (500 °C) KPHI variant using autogenous NH3 pressure.
• Characterization using transient absorption spectroscopy to study charge carrier dynamics.

Main Results:

• The engineered KPHI exhibited nanoscale fragmentation and controlled cyano defect introduction.
• The modified KPHI demonstrated enhanced photocatalytic performance for oxygen reduction, achieving high apparent quantum yields (AQY).
• Cyano defects were confirmed to facilitate efficient charge separation and accelerate reaction kinetics, with electrons localizing at -C≡N sites.

Conclusions:

• Nanostructural engineering and defect control in KPHI significantly enhance its photocatalytic activity for H2O2 production.
• The developed method provides a generalizable approach for tailoring ionic carbon nitrides.
• A sustainable, low-temperature synthesis route for high-performance KPHI was established.