Facile in situ construction of mediator-free direct Z-scheme g-C3N4/CeO2 heterojunctions with highly efficient photocatalytic activity

Designing a mediator-free direct Z-scheme heterojunction photocatalyst is a highly effective strategy for environmental purification and hydrogen generation from water. Herein, hierarchical g-C3N4/CeO2 Z-scheme heterojunctions are successfully prepared via a facile calcination method without using any templates. This feasible strategy combines the morphology control with the formation of direct Z-scheme heterojunction. The resultant hierarchical g-C3N4/CeO2 heterojunction is much more active than the commercial Degussa P25 under visible light irradiation, validated by the high methylene blue degradation rate of 0.246 h(-1), which is about 4.8, 8.8 and 30.8 times higher than that of commercial Degussa P25 (0.051 h(-1)), bulk g-C3N4 (0.028 h(-1)) and hierarchical CeO2 (0.008 h(-1)), respectively. The Z-scheme charge transfer mechanism across the heterojunction is verified by the active species trapping and producing experiments, as well as ab initio calculations. The hierarchical structures with large exposure surface, more efficient light harvesting, and a direct Z-scheme heterojunction for efficient photoinduced charge carriers transfer and separation across the interfacial domain of g-C3N4/CeO2 heterostructures, are the key to attractive photocatalytic performance. This work provides a promising approach to design high-efficient mediator-free direct Z-scheme photocatalysts by morphology control and heterojunction engineering.