Synthesis and characterization of porous zinc oxide nano-flakes film in alkaline media

In this study, porous zinc oxide nano-flakes were successfully synthesized by anodization method on zinc substrate in a 0.025 M NaOH and 0.05 M NH4Cl solution with the voltage of 10 V at room temperature. The field emission scanning electron microscopy’s (FESEM) images show the structural evolution during 90 min of the anodization process. They also demonstrate the dependency of growth of ZnO flakes on the grains of the zinc substrate. Regarding FESEM images and possible chemical reactions taking place during the anodization process, a growth mechanism and sequences for the formation of ZnO have proposed. The Pourbaix diagram also confirmed this possible mechanism. The elemental  and phase analysis conducted on films proved the formation of the ZnO after the anodization process. The cyclic voltammetry showed the oxidation of zinc into zinc oxide is related to the -1.28 V peak and the peak of zinc oxide reduction is situated at -1.48 V.  The band gap of anodized zinc foil was calculated to be 3.24 eV. The photocatalytic activity of synthesized thin films also was studied and the ImageJ software analysis showed a strong correlation between the photocatalytic activity and the portion of porosity in the synthesized films