Probing Shallow Defect States-Induced Photocarrier Behavior of G-C₃N₄ on a Femtosecond Timescale Toward Photocathodic...

Area of Science:

• Materials Science
• Photocatalysis
• Surface Chemistry

Background:

• Defect engineering in graphitic carbon nitride (g-C3N4) is crucial for photocatalysis.
• Improperly controlled defects can hinder charge transfer efficiency.

Purpose of the Study:

• To introduce shallow defect states into S-doped and C-vacant g-C3N4 (CN-ES) using a dual-solvent method.
• To enhance photocarrier transport and separation efficiency in g-C3N4.

Main Methods:

• Dual-solvent-assisted synthesis of S-doped and C-vacant g-C3N4 (CN-ES).
• Femtosecond spectroscopy to analyze photoexcitation and charge relaxation times.
• Electrochemical measurements for photocathodic protection evaluation.
• Theoretical calculations (DFT) to understand electronic structure.

Main Results:

• Introduced shallow defect states in CN-ES reduced photoexcitation time and charge relaxation to 35.84 ps.
• Shallow defects improved photocarrier separation by acting as an electron reservoir (323.78 ps electron lifetime).
• Suppressed non-radiative recombination, resulting in a slow pseudo-first-order rate constant (0.053 s⁻¹).
• CN-ES demonstrated excellent photocathodic protection for 304 stainless steel with 96.5% potential retention.

Conclusions:

• Optimized shallow defect states in CN-ES significantly accelerate charge transfer kinetics and enhance photocarrier separation.
• Theoretical calculations confirm improved charge distribution and electric fields within CN-ES.
• CN-ES shows great potential for large-scale applications, particularly in the photocathodic protection of metals.