O-doped g-C3N4 prepared in pyridine for efficiently photocatalytic hydrogen production.

Oxygen-doped g-C₃N₄ with pyridine ring (POCN) was synthesized by easily thermal polymerization of urea, pyridine solution, and ammonium acetate to improve photocatalytic hydrogen production. The experimental results indicate that pyridine was incorporated into the tri-s-triazine structure of g-C₃N₄. The O atoms were modified to g-C₃N₄ by replacing the N atoms (C-N=C) of the triazine ring. The photocatalytic activity for the hydrogen production rate of optimized POCN was 1018 µmol g^-1 h^-1, approximately 30 times higher than that of bulk g-C₃N₄ (CN) under visible light irradiation (λ > 420 nm). The high stability of POCN was confirmed through cycling tests for 30-h, XRD patterns, and SEM images. The pyridine incorporation can significantly enhance surface charge transfer efficiency. The oxygen modification can greatly promote visible light absorption (600 nm) and photogenerated electron-hole pairs separation. This work provides a suitable strategy to synthesize g-C₃N₄ based on metal-free photocatalysts for highly efficient photocatalytic hydrogen generation performance.