Doping effects of Co2+ ions on ZnO nanorods and their photocatalytic properties

A series of Zn1-xCoxO nanorods with dopant content ranging from x = 0.00 to 0.10 was prepared by a wet chemical method. All Zn1-xCoxO samples were investigated by x-ray diffraction, transmission electron microscopy, energy-dispersion x-ray line mapping analysis, and UV-visible absorption spectroscopy. It was found that Co2+ ions were homogeneously substituted for Zn2+ ions in ZnO nanorods. Rhodamine B degradation was used as a probe reaction to evaluate the effect of Co2+ doping on ZnO nanorods and photocatalytic performance under UV light and visible light irradiation. Co2+ ions acted as the trapping or recombination centers for electrons and holes, leading to a reduction in photodegradation efficiency under UV light illumination. Alternatively, Co2+ ions enhanced the optical absorption and produced the photoinduced carriers under visible illumination in terms of two charge transfer transitions involving Co2+ ions. Consequently, Co2+ ions substituted in the lattice of ZnO nanorods significantly improved the visible light photocatalytic activity.