Study of effect of high annealing temperature on the photocatalytic activity of ZnO thin films prepared by dip-coating method

In this work, we discuss the effect of annealing temperature on the structural, morphological optical and photocatalytic properties of zinc oxide (ZnO) thin films prepared by using dip-coating technique on porous ceramic substrates at different annealing temperatures of 400 °C, 500 °C, 600 °C, and 700 °C for 2 h. The photocatalytic activity of the prepared ZnO photocatalysts was examined by evaluating the degradation of Orange II (OII) as a model of dyes under light irradiation. ZnO photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV–visible absorption spectroscopy. SEM analysis revealed that the annealing temperatures greatly affected the grain size and the topography of ZnO surfaces. XRD results showed that all samples have a polycrystalline nature with a hexagonal wurtzite structure. The experimental data demonstrated that the average crystallite size of the prepared ZnO thin films varied from 15 to 24 nm with the increase of the annealing temperatures from 400 °C to 700 °C. The UV–Vis data indicated an enhancement in the absorbance of ZnO thin films across the ultraviolet range with increased annealing temperatures. The photodegradation rate increased to 94.7% by increasing the annealing temperatures.