Unraveling the presence and positions of nitrogen defects in defective g‐C3N4 for improved organic photocatalytic degradation: insights from experiments and theoretical calculations

Journal article

In this work, nitrogen-defective $g$-C$_3$N$_4$ with different nitrogen defect densities is synthesized for ciprofloxacin photocatalytic degradation. Compared with pristine $g$-C$_3$N$_4$, $g$-C$_3$N$_4$ etched with NaBH$_4$ for 1~h exhibits an approximately ten-fold increase in the rate constant of ciprofloxacin (CIP) degradation. The combined experimental analysis and theoretical calculations reveal that nitrogen defects can be incorporated into $g$-C$_3$N$_4$ at all nitrogen sites, and that the C--N=C configuration is the most susceptible site. By incorporating nitrogen defects to induce defect states between the conduction band (CB) and valence band (VB), the electronic and band structures are tuned. The induced defect states can be downshifted to approach the valence band; with increased nitrogen defect density within optimum ranges, excited electrons are accommodated, leading to a narrowed bandgap, extended light absorption capability, and enhanced charge-carrier separation and transfer efficiency. The $g$-C$_3$N$_4$ etched by NaBH$_4$ for 2 h, with over-introduced nitrogen defects, exhibits declined performance due to structural deterioration, and the over-downshifted defect states become new recombination centers for charge carriers.

Authors: Liu, Y; Chen, X; Kamali, M; Rossi, B; Appels, L

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Wiley
• Journal: Advanced Functional Materials
• Volume: 34
• Issue: 40
• Article number: 2405741
• Publication date: 2024-06-28
• Acceptance date: 2024-06-06
• DOI: 10.1002/adfm.202405741
• EISSN: 1616-3028
• ISSN: 1616-301X
• Language: English
• Keywords: quantum size effect; defect state; g-C3N4; nitrogen defect