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

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 degrees 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 m(2) 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. (C) 2013 Elsevier B.V. All rights reserved.