Rational Design of Z-Scheme System Based on 3D Hierarchical CdS Supported 0D Co9S8 Nanoparticles for Superior Photocatalytic H2 Generation

Developing a durable and efficient photocatalyst for H2 evolution is highly desirable to expedite current research on solar–chemical energy conversion. In this work, we rationally designed and synthesized a direct Z-scheme system based on three-dimensional hierarchical CdS decorated with Co9S8 nanoparticles toward photocatalytic H2 evolution. The composition, microstructure, and optical properties of the hybrids were thoroughly investigated. Photocatalytic performances revealed that the optimized CdS/Co9S8-15 composite exhibited the highest H2-evolution rate of 5.15 mmol h–1 g–1, which is approximately 6.8 and 257.5 times that of CdS and Co9S8, respectively. In addition, this novel composite catalyst also displayed long-term stability without apparent debasement in photocatalytic activity. On the basis of the analysis of UV–vis diffuse reflectance spectroscopy, photocurrent response, electrochemical impedance spectra, and photoluminescence, the reinforced H2 evolution performance of the CdS/Co9S8 samples was attributed to a synergistic effect including boosted light absorption capacity, increased separation and transfer efficiency of photogenerated electron/hole pairs, as well as much stronger reducibility of electrons in the conduction band of Co9S8. Finally, the photocatalytic mechanism for this composite was proposed and discussed in detail.