A comparative study on the photocatalytic efficiency of ZnO thin films prepared by spray pyrolysis and sol–gel method

Nanocrystalline ZnO thin films are deposited on aluminum foil and glass substrates by two different chemical methods: (i) polymer modified spray pyrolysis and (ii) sol–gel dip-coating from zinc acetate complex solutions. The ZnO films are characterized by means of scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction. The films obtained by procedure (i) possess a porous structure, while the films obtained by procedure (ii) have ganglia on the surface. The influence of the thermal treatment temperature (350 or 450 °C) on the film microstructure and photocatalytic efficiency toward the organic dyes malachite green (MG) and reactive black (RB5) is also investigated. The films obtained by both methods have a better photocatalytic activity in the degradation of RB5 compared to MG due to the weaker NN bond in comparison with the CC bond between the central carbon atom and N,N-dimethylaminobenzyl in MG.