Characterization of photocatalytic hybrid TiO2–WOX thin films deposited via co-sputtering

Abstract

Photocatalytic hybrids of titanium dioxide (TiO2) and tungsten oxide (WOX) can exhibit high photocatalytic activity under weak ultraviolet (UV) and visible-light irradiation. In this study, hybrid TiO2–WOX thin films deposited via co-sputtering are characterized using radiofrequency sputtering at various compositions, and their photocatalytic activity in the degradation of a methylene blue solution is evaluated. X-ray photoelectron spectroscopy measurements show enhanced W(4f) and decreased Ti(2p) signal intensities with increasing WOX content. Further, chemical shifts toward lower binding energies are observed as the compositions of TiO2 and WOX become equivalent. X-ray diffraction analysis reveal decreased anatase TiO2 peaks and monoclinic WOX peaks with the formation of amorphous structures as the compositions of TiO2 and WOX become equivalent. Atomic force microscopy images show homogeneous and flat structures on the surfaces of the hybrid TiO2–WOX thin films. The deposition rate decreases with decreasing WOX sputter power, whereas the optical bandgap decreases with increasing WO3 content. Furthermore, the photocatalytic activity under UV irradiation improves with increasing TiO2 content, whereas that under visible-light irradiation improves with increasing WOX content. This approach can provide the guidelines to fabricate the high-performance photocatalytic materials that can be used in different condensed thin-film devices.