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Porous Mn-doped ZnO (ZnO:Mn) nanoparticles with an average diameter of ca. 21 nm were prepared by a simple and cheap solvothermal process involving no templates, post-synthetic annealing or etching. The particles produced were characterized by XRD, Raman spectroscopy, SEM, TEM, XPS, diffuse reflectance spectroscopy and BET surface area measurements and the effects of Mn 2+-doping on the structural, optical and photocatalytic properties of ZnO particles were investigated. The particles doped with 3 mol% Mn 2+ were found to exhibit the highest catalytic activity toward the photodegradation of the Orange II dye under solar light irradiation. Our results demonstrate that Mn 2+-doping shifts the optical absorption to the visible region, increases the specific surface area of the photocatalyst and reduces the recombination of electron-hole pairs. The influence of various operational parameters (amount of catalyst, concentration of dye and pH) on the photodegradation and the photocatalytic mechanism were studied. Finally, we demonstrated that the ZnO:Mn photocatalyst is stable and can be easily recycled up to ten times without any significant decrease in photocatalytic activity.

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SummaryCe-doped ZnO (ZnO:Ce) nanorods have been prepared through a solvothermal method and the effects of Ce-doping on the structural, optical and electronic properties of ZnO rods were studied. ZnO:Ce rods were characterized by XRD, SEM, TEM, XPS, BET, DRS and Raman spectroscopy. 5% Ce-doped ZnO rods with an average length of 130 nm and a diameter of 23 nm exhibit the highest photocatalytic activity for the degradation of the Orange II dye under solar light irradiation. The high photocatalytic activity is ascribed to the substantially enhanced light absorption in the visible region, to the high surface area of ZnO:Ce rods and to the effective electron–hole pair separation originating from Ce doping. The influence of various experimental parameters like the pH, the presence of salts and of organic compounds was investigated and no marked detrimental effect on the photocatalytic activity was observed. Finally, recyclability experiments demonstrate that ZnO:Ce rods are a stable solar-light photocatalyst.

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