Synergistic Promotion Effect of ZnCoS Solid Solution and Co1-xS on Photocatalytic Hydrogen Production of the CdS Composite.

Photocatalytic reactions over effective photocatalysts are attractive to explore clean hydrogen energy from water with the utilization of solar energy. Ternary Co1-xS@ZnCoS/CdS (ZCS/CdS) composites are constructed as photocatalysts through the hydrothermal formation of Co1-xS and ZnCoS nanoparticles on CdS nanorods. Superior to the binary Co1-xS/CdS composite, ZCS/CdS shows the improved photocatalytic activity with a hydrogen production rate of 58.4 mmol·g-1·h-1, which is 31.4 and 2.1 times higher than those of CdS and Co1-xS/CdS, respectively. Different from binary Co1-xS/CdS, the participation of a small amount of zinc favors the formation of ZnCoS solid solution in ZCS/CdS. A synergistic promotion effect of ZnCoS and Co1-xS is confirmed due to tight heterojunctions among Co1-xS, ZnCoS, and CdS in ZCS/CdS. The unique heterostructure of ZCS/CdS benefits its enhanced absorption ability of visible light, accelerating the separation of photoinduced electron-hole pairs and the electron transfer. ZCS/CdS exhibits the strong reduction ability and superior photocatalytic stability due to the role of double Z-scheme electron transfer pathways in the ternary composite. This work provides a suitable way to tune noble metal-free composite photocatalysts for efficient H2 production.