Electronic Structure and Photocatalytic Activity of Dual <i>Z</i>-Scheme CdS@Bi₂S₃–MoS₂ Heterostructures with a Full Spectrum

Two-dimensional Bi2S3 is considered a better photocatalyst when combined with CdS. To deeply understand electronic structures between CdS and Bi2S3, CdS@Bi2S3 core–shell nanorods (NRs) were synthesized with a two-step hydrothermal method, and CdS@Bi2S3–MoS2 composites were obtained with MoS2 nanoparticles decorated on the surface of CdS@Bi2S3 NRs. Then, the energy band alignments in CdS@Bi2S3–MoS2 were constructed from XPS and UPS measurements, and dual z-scheme CdS@Bi2S3–MoS2 heterostructures were confirmed from charge transfer with electron spin resonance (ESR) signals of •O2– and •OH. Finally, the photocatalytic hydrogen activities were carried out with the prepared samples. The results showed that the optimized CdS@Bi2S3 core–shell NRs have a hydrogen production rate of 4.29 mmol·h–1·g–1, which is 8.4 times higher than that of the pure CdS nanorods, and the optimized CdS@Bi2S3–MoS2 heterostructure has a hydrogen production rate of 8.72 mmol·h–1·g–1, which is 17 times higher than that of the pure CdS NRs. The enhanced photocatalytic activity can be ascribed to the dual z-scheme heterostructure and full-spectrum absorption; the former is favorable for the efficient separation of the photogenerated electron–hole pairs, and the latter is beneficial to the production of more photogenerated carriers. The studies will be helpful to understand the electronic structures of Bi2S3 and the related heterostructures.