Efficient photocatalytic hydrogen evolution by in situ construction of Nb4+ charge-carrier channels in hollow porous tubular C3N4 and Nb2O5 Z-scheme heterojunctions

Optimizing heterojunction structure is an important way to improve photocatalytic activity. Herein, we report a novel hollow tubular C₃N₄/Nb⁴⁺/Nb₂O₅ nanoparticle Z-Scheme heterojunction, by introducing Nb⁴⁺ ions into Nb₂O₅ through a reducing atmosphere during C₃N₄ thermal polymerization. The optimized heterostructure showed outstanding photocatalytic hydrogen evolution activity under both UV–vis (14.93 mmol g⁻¹ h⁻¹) and Vis (5.22 mmol g⁻¹ h⁻¹) lights. The photocatalytic hydrogen evolution activity under UV–vis light is 26.6 and 4.75 times that of bulk C₃N₄ (CN) and hollow tubular C₃N₄ (HCN), respectively. The increased photocatalytic activity can be attributed to the larger specific surface area, more active sites, and enhanced light absorption capacity of the composite. Crucially, the introduction of Nb⁴⁺ ions as the charge-carrier transport channels in the Z-scheme heterostructure improves the efficiency of photogenerated charge-carrier separation. This study provides a useful design strategy for Z-Scheme photocatalytic heterojunction structures that can utilize solar light more efficiently.