Precise Defect Engineering on Graphitic Carbon Nitrides for Boosted Solar H₂ Production

Area of Science:

• Materials Science
• Photocatalysis
• Semiconductor Engineering

Background:

• Graphitic carbon nitride (g-C3N4) shows promise for solar applications but suffers from limited solar utilization due to defect-related charge recombination.
• Effective defect engineering is crucial to overcome these limitations and improve photocarrier separation efficiency.

Purpose of the Study:

• To develop a novel defect engineering strategy for g-C3N4 to enhance its photocatalytic performance.
• To precisely control defect states and surface properties for improved solar energy conversion.

Main Methods:

• A dual-solvent-assisted synthesis approach was employed using ethylene glycol (EG) and molten sulfur.
• This method precisely introduced sulfur (S) dopants and nitrogen (N) vacancies, creating shallow defect states in g-C3N4.
• Characterization included measurements of electron-trapping resistance and surface carrier decay kinetics.

Main Results:

• The synthesized defective g-C3N4 (DCN-ES) exhibited shallow defect energy levels, acting as an electron reservoir to suppress recombination.
• Optimized surface states showed high electron-trapping resistance (9.56 × 10^3 Ω cm^2) and slow carrier decay kinetics (0.057 s^-1).
• DCN-ES achieved a remarkable hydrogen (H2) evolution rate of 4219.9 µmol g^-1 h^-1, a 29.1-fold increase over unmodified g-C3N4.

Conclusions:

• The developed defect engineering strategy effectively creates shallow defect states and optimizes surface properties in g-C3N4.
• This approach significantly enhances photocarrier separation and suppresses recombination, leading to superior photocatalytic activity for hydrogen production.
• The findings offer a promising pathway for advancing solar fuel generation using engineered semiconductor materials.