Nitrogen defect engineering and π-conjugation structure decorated g-C₃N₄ with highly enhanced visible-light photocatalytic hydrogen evolution and mechanism insight

The precise molecular tunability strategy is deemed to have great potential to improve the photocatalytic performance of metal-free photocatalysts for applying in hydrogen evolution but remains a formidable task. We herein cover a logical design for integrating N defect engineering and π-conjugation structure into g-C₃N₄. The photocatalytic hydrogen evolution rate of up to 1541.6 μmol g⁻¹ h⁻¹ is acquired over the optimum DCN350, which has 7.5-fold increase over primal g-C₃N₄ (205.9 μmol g⁻¹ h⁻¹). The experimental study and density functional theory (DFT) investigations confirm that DCN350 with N defects not only can shorten band gaps for expanding the light absorption range via optimizing the electronic band structure, but also act as active sites for facilitating hydrogen evolution reaction. Besides, the –C≡N as strong electron-withdrawing functional group can make the isolated valence electrons delocalized to drive the charge spatial separation. Therefore, the light absorption capacity and charge separation/transfer of g‐C₃N₄ can be flexibly mastered via changing calcination temperature of g-C₃N₄ and NaBH₄. Overall, this study provides an opportunity for having a deep understanding the role of structural defects on ameliorating the photocatalytic evolution hydrogen activity.