Molten salt-assisted synthesis of carbon nitride with defective sites as visible-light photocatalyst for highly efficient hydrogen evolution

• Published in: Applied catalysis. B, Environmental Environmental, 2025-03, Vol.362, p.124711, Article 124711
• Main Authors: Quan, Yongkang, Li, Jianna, Li, Xingzhou, Chen, Rongxing, Zhang, Yingzhen, Huang, Jianying, Hu, Jun, Lai, Yuekun
• Format: Article
• Language: English
• Subjects: Carbon nitride; C≡N; Effective charge separation; Nitrogen defects; Photocatalytic H2 evolution
• ISSN: 0926-3373
• DOI: 10.1016/j.apcatb.2024.124711

The low light absorption capacity, fast recombination of photogenerated carriers and slow H+ reduction kinetics of carbon nitride severely limit its application in photocatalytic research. What's more, the challenge remains to efficiently utilise photogenerated electrons. In this work, sulfur (S) self-doped carbon nitride (SCN) was formed by thermal polymerisation, and the introduction of S stimulated the electron delocalisation of the active site and optimised the absorption of visible light by the carbon nitride. The introduction of defects and cyano (-C≡N) groups optimises the surface atomic and electronic structure of SCN, enhances photogenerated electron trapping and greatly suppresses charge recombination. The n-π* electron jump of the lone pair of electrons at the defect site gives rise to a new absorption band that broadens the response to visible light. The H2 evolution rate of SCNV under visible light reached 3437 μmol g−1 h−1, which was about 3.0 times higher than that of SCN (1148 μmol g−1 h−1). Density Functional Theory (DFT) calculations further show that the introduction of defects and -C≡N lowers the energy barrier of *H, enhances carrier separation, and forms an electron-rich structure, which effectively promotes the utilisation of photogenerated electrons and photocatalytic H2 evolution efficiency. [Display omitted] ●The introduction of nitrogen defects and -C≡N changes the electron transfer path.●SCNV has stronger thermodynamic driving force and electron reduction ability.●The electron-rich structure makes the charge density of SCNV more localised.●Excellent photocatalytic H2 evolution was achieved with low energy consumption.