Enhanced Photocatalytic Activity by Aligned WO3/TiO2 Two-Layer Nanorod Arrays

The photocatalytic and structural properties of TiO2/WO3 two-layer nanostructures made by electron beam deposition were studied and compared with single-layer TiO2 nanostructures. Three different two-layer structures, thin film, tilted nanorods, and vertical nanorods, were fabricated by a normal deposition, oblique angle deposition, and glancing angle deposition. The as-deposited and annealed samples at T-a = 300 degrees C and T-a = 400 degrees C, respectively, were studied by SEM, XRD, Raman spectroscopy, and UV-vis spectrophotometry. The photocatalytic properties of those samples were investigated and found to be improved significantly by increasing the surface and interfacial area, annealing at a proper temperature, the enhanced charge separation due to the WO3-TiO2 coupling, and the arrangement of the two layers. The optimal structure was found to be the two-layer vertical TiO2/WO3 nanorods after annealing at T-a = 300 degrees C, which had a photodegradation rate about 10 times higher than a single-layer TiO2 vertical nanorod array.