Tuning of the UV photocatalytic activity of ZnO using zinc ferrite(III): Powders and thin films prepared of powders

Nanostructured thin films and powders of ZnO mixed with zinc ferrite(III), ZnFe2O4, are prepared, characterized and tested for the first time in the photocatalytic degradation of dye aqueous solutions. The decolorization kinetics of malachite green in water upon UV-light illumination is studied as a model system. The ZnO and ZnO/ZnFe2O4 powders are first tested as photocatalysts in the form of slurry. Then thin films of the same materials are prepared from polyethylene glycol/alcohol dispersions of the powders on glass substrates using dip coating. The films are characterized by means of scanning electron microscopy, X-ray diffraction and specific surface area before and after annealing. Their photocatalytic activity is investigated and compared with that of the respective powders. The initial concentration of malachite green, the amount of catalyst, and the molar ratio of ZnFe2O4/ZnO are varied during the experiments. It is found that increasing the amount of ZnFe2O4 with respect to ZnO lowers the photocatalytic activity in comparison with pure ZnO for both films and powders under UV-light illumination. The observed nonlinear dependence on the zinc ferrite content can be used as a means for the fine tuning of the activity of ZnO catalysts.