Development of multi-bandgaps for TiO_1.7 thin film via mixing with ZnO: efficient solar photocatalysis approach

Abstract Thin films (8 nm) of pure and mixed metal oxides (TiO 1.7 and ZnO) were prepared by plasma enhanced atomic layer deposition. These thin films have x-ray amorphous structure, as confirmed by grazing-incidence x-ray diffraction and scanning electron microscopy. Mixing of TiO 1.7 and ZnO could lead to development of multi-band gaps. For example, TiO 1.7 (59%)ZnO(41%) has 4 indirect band gaps: 3.48, 2.81, 2.62 and 1.15 eV. In addition, this mixed metal oxide has higher absorption coefficient and red shift in the absorption edge. This leads to improving the solar photocatalytic activity by about 3.5 times that of the pure TiO 1.7 to treat the water from the organic dyes such Levafix Brilliant Red. This can be attributed to increasing the percentage of the non-lattice oxygen from 30% to 77.4% with the addition of ZnO with 41% to the Titania thin film as presented by the x-ray photoelectron spectroscopy analysis. Also, the enhanced photocatalytic activity can be due to the increased lifetime and decreased recombination rate of the photogenerated charge carriers in the multiband gap mixed metal oxide.