Visible-light-active photocatalytic thin film by RF sputtering for hydrogen generation

Visible-light absorbing TiO₂ (vis-TiO₂) and WO ₃ (vis-WO₃) photocatalytic thin films were prepared by radio-frequency magnetron sputtering. The effect of heat treatment on thin film properties was investigated. Instrumental analyses such as X-ray diffraction, scanning electron microscopy-energy dispersive X-ray spectroscopy, and ultraviolet-visible absorption spectrometry were performed to reveal the crystallinity, surface morphology, chemical composition, and light absorption of the prepared thin films. To further enhance the photoactivity of the prepared thin films, a dual-layer photoelectrode (DLP) that consists of both vis-TiO ₂ and vis-WO₃ was fabricated. Moreover, photoactivities of the prepared single and dual-layer photoelectrodes under both ultraviolet and visible-light irradiations were evaluated by conducting photovoltammetry as well as water-splitting reaction in an H-type reactor. It was demonstrated that the H₂ and O₂ yields obtained from water-splitting reaction are consistent with the photocurrent results, showing that DLP is more photoactive than single-layer photoelectrode. The enhanced performance of DLP is mainly attributed to the improved charge separation of the dual-layer structure.