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-C 3 N 4 /CeO 2 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-C 3 N 4 /CeO 2 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-C 3 N 4 (0.028 h −1 ) and hierarchical CeO 2 (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-C 3 N 4 /CeO 2 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.
Hexagonal-like zinc oxide (ZnO)/silver (Ag) composite was successfully synthesised by a flux/solvothermal route, and Ag nanoparticles are loaded on ZnO. Compared with pure ZnO, the attachment of Ag on ZnO can significantly increase visible-light absorption and reduce photoluminescence emission intensity. The photocatalytic performance of ZnO/Ag composite was evaluated by the degradation of Rhodamine B solution under ultraviolet (UV) light and visible light irradiation. The degradation rate of ZnO/Ag composite is obviously improved compared with pure ZnO and the commercial TiO 2 (P25) and is more than 2.5 and 2.9 times faster than that of pure ZnO under the UV and visible light irradiation, respectively. The enhanced photocatalytic activity of ZnO/Ag composite under UV irradiation was ascribed to the formation of Schottky barriers between Ag particles and ZnO. However, the superior photocatalytic activity under visible light irradiation could be attributed to the surface plasmon resonance of Ag particles.
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