Single-step sensitization of reduced graphene oxide sheets and CdS nanoparticles on ZnO nanorods as visible-light photocatalysts

• Facile fabrication of graphene and CdS sensitized ZnO nanorods.
• Effective photodegradation of MB under visible light irradiation.
• Excellent separation of photogenerated electron-hole pairs.

Novel composite photocatalysts composed of reduced graphene oxide (RGO) sheets, CdS nanoparticles (CNPs), and ZnO nanorods were developed using a simple low-temperature chemical approach. The RGO sheets and CNPs were sensitized via single-step chemical bath deposition at 70 °C. Because of the incorporation of RGO into the CdS and ZnO structures, the photodegradation performance toward methylene blue (MB) degradation under visible light illumination was significantly improved compared with that of just CdS and ZnO. The highest kinetic rate constant (k = 0.028 min−1) using 0.20 wt% of added RGO was four times higher than that without graphene. This composite degraded MB within 40 min. Such improved performance resulted from effective separation of electron-hole pairs by the RGO sheets. Photoluminescence quenching, increased optical absorbance, and high specific surface area (23.08 m2 g−1) also contributed to the high degradation efficiency. An energy level diagram was constructed to explain how the RGO sheets minimized the recombination rate. The developed RGO–CdS–ZnO composites have a potential application in water purification devices.

Schematic of electron transportation from CdS nanoparticles to ZnO naorods and graphene sheets for MB photodegradation.Figure optionsDownload as PowerPoint slide