Regulation of carboxyl groups and structural defects of graphitic carbon nitride via environmental-friendly glucose oxidase ring-opening modulation

• Published in: Applied catalysis. B, Environmental Environmental, 2021-11, Vol.297, p.120441, Article 120441
• Main Authors: Zhang, Zhihao, Cui, Lifeng, Zhang, Yan, Klausen, Lasse Hyldgaard, Chen, Mengya, Sun, Di, Xu, Suyun, Kang, Shifei, Shi, Jiyong
• Format: Article
• Language: English
• Subjects: Carbon; Carbon nitride; Carboxyl group; Carboxyl groups; Charge separation; Chromium; Defects; Detoxification; Electrochemistry; Electronic structure; Enzymes; Functional groups; Glucose; Glucose oxidase; Graphitic carbon nitride; Modulation; NMR; Nuclear magnetic resonance; Photocatalysis; Photocatalysts; Polymers; Ring opening; Separation; Structural defect engineering; X ray photoelectron spectroscopy
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2021.120441

[Display omitted] •Biological enzyme glucose oxidase was firstly introduced in the O-site defects engineering of g-C3N4 at 37 °C.•Optimized g-C3N4 photocatalysts with ring-opening defects and enriched carboxyl groups was successfully achieved.•Synergetic structural and carboxyl group defects determines the good charge separation and photocatalytic performance.•The enzymatic defects regulation effect can be boosted on the O-enriched g-C3N4 sample.•This green enzyme method is promising in the scale-up activation of polymer and photoelectronic materials. Structural defects and surface functional groups defects engineering in the graphitic carbon nitride (g-C3N4) polymer semiconductor usually has great benefit in optimizing its electron structure and photocatalytic performance. In this study, one type of carboxyl group defects-grafting g-C3N4 was prepared through glucose oxidase treatment on the initial O sites in the g-C3N4, which played multi-functional roles in the generation of carboxyl groups and melon structure defect. FT-IR, XPS and 13C NMR analysis verified the presence of highly favorable carboxyl groups, which was beneficial to the fast separation and migration of photogenerated carriers. The singularity of enzyme mediated defects control of carbon nitride materials was greatly boosted on O-enriched g-C3N4 (OCN) further supporting the overall O sites ring-opening hypothesis. The glucose oxidase (GOD) treated reconstructed g-C3N4 photocatalysts showed narrowed band gaps and fast charge separation ability as verified by UV–vis DRS and electrochemical tests. As a result, the optimized photocatalyst (GOD-OCN-3d) showed a high Cr(VI) photocatalytic detoxification rate of 99 %, which was 6.6 times higher than that of raw g-C3N4 (15 %) in 120 min. These findings open the understanding on precise molecular defects modulation of g-C3N4 via an environmental-friendly enzyme treatment approach, as well as providing a new avenue for understanding the function of structural defects of photocatalysts on prompting charge separation.