Effect of the mixing rate on the morphology and photocatalytic activity of ZnO powders prepared by a precipitation method

The urchin-like shape of ZnO powders was prepared by mixing of Zn2+ and NaOH solutions at various mixing rates. In this work, ε-Zn(OH)2 was the first precipitant that was subsequently transformed to ZnO in the alkaline medium during heating. The size of the urchin-like shape of the ZnO powder decreased with a decrease of the mixing rate. The large urchin-like shape also had a large diameter of its hexagonal facet (0 0 0 1) and showed the highest photocatalytic degradative activity on methylene blue.

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► Alkaline medium is a important factor to transform the ε-Zn(OH)2 to ZnO.
► The urchin-like ZnO grow from the surface of the ε-Zn(OH)2 crystals.
► The photocatalytic activity depends on the population of the (0 0 0 1) facet.