Rational Design of Z-Scheme System Based on 3D Hierarchical CdS Supported 0D Co9S8 Nanoparticles for Superior Photocatalytic H-2 Generation

Developing a durable and efficient photo catalyst for H-2 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 H-2 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 H-2-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 H-2 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.