Photocatalytic activities of wet oxidation synthesized ZnO and ZnO–TiO₂ thick porous films

Highly porous zinc oxide (ZnO) film was produced by using reactive magnetron sputtering zinc target followed by wet oxidation. Titanium dioxide (TiO₂) was mixed to the porous films by using either TiO₂ target magnetron sputter deposition or sol-spin method. The film thickness could reach 50 μm with uniform porosity. On the sputtering prepared ZnO–TiO₂ film surface, fine nanorods with small anatase TiO₂ nano-clusters on the tips were observed by SEM and TEM, and the titanium (Ti) composition was determined by XPS as 0.37%. The sol-spin treatment could increase the Ti composition to 4.9%, with reduced pore size compared to the untreated ZnO porous film. Photoluminescence measurements showed that the Ti containing porous film has strong ultraviolet-visible light emission. In the photo-catalysis testing, ZnO and ZnO–TiO₂ have similar photo-catalysis activity under 365 nm UV irradiation, but under visible light, the photocatalysis activities of ZnO–TiO₂ films were twice higher than that of ZnO porous film, implying promising applications of this porous oxide composite for industrial and dairy farm wastewater treatment.