Investigation of photo-electrochemical response of iron oxide/mixed-phase titanium oxide heterojunction toward possible solar energy conversion.

Photocatalysts are part of key strategies to enable green fuel. Photocatalysis and water splitting could be a promising solution to challenges associated with the intermittent nature of sunlight as a huge energy source on Earth. In this study, photo-electrochemical performance and behavior of mixed-phase titanium oxide and iron oxide heterojunction (Ti-TiO x (High-voltage)-FeO x electrode) are compared to the photo-electrochemical performance and behavior of titanium oxide nanotubes with the rutile phase and iron oxide heterojunction (TiO x -nanotubes (H 2 SO 4 /KF)-FeO x electrode). The results of photo-electrochemical experiments show that the application of stabilization potential and the presence/absence of dissolved oxygen could not be considered as significant factors affecting the photo-electrochemical properties of the Ti-TiO x (High-voltage)-FeO x and TiO x -nanotubes (H 2 SO 4 /KF)-FeO x electrodes. The Ti-TiO x (High-voltage)-FeO x electrode shows an anodic photo-electrochemical response in wavelengths shorter than 530 nm and cathodic photo-electrochemical response in wavelengths longer than 530 nm. However, the Ti-nanotubes (H 2 SO 4 /KF)-FeO x electrode consistently exhibits the anodic photo-electrochemical response. Both of the prepared heterojunctions are further characterized through Scanning Electron Microscopy, Energy-dispersive X-ray Spectroscopy, Diffuse Reflectance UV–Vis Spectroscopy, X-ray Diffraction, and Attenuated Total Reflectance Spectroscopy methods. These experiments show that despite different morphologies observed in SEM imaging data, the deposited iron oxide layers on both mixed-phase titanium oxide and titanium oxide nanotubes share the same hematite phase structure. However, only iron oxide electro-deposited on the surface of the mixed-phase titanium oxide, which contains both anatase and rutile phases, with vacant sites of oxygen, exhibits un-expected anodic and cathodic photo-electrochemical responses. Furthermore, according to the results of the characterization and photo-electrochemical investigations, the different chemical environment of mixed-phase titanium oxide, and the possible formation of different types of heterojunction structures in mixed-phase titanium oxide and iron oxide, in contrast to the titanium oxide nanotubes and iron oxide, might be considered the possible discernible reasons for the observed different photo-electrochemical responses. This paper sheds new light on photo-electrochemistry of iron oxide/mixed-phase titanium oxide heterojunction for possible solar energy conversion. In this study, photo-electrochemical performance and behavior of mixed-phase titanium oxide and iron oxide heterojunction were investigated. Image 1 • Photo-electrochemical studies conducted on mixed-phase titanium oxide and iron oxide. • The photocatalysts showed a cathodic response contrary to n-type nature of hematite. • Mixed-phase TiO 2 imposes different chemical conditions on iron oxide photocatalyst. • Photo-electrochemistry of the compound confirms the energy band level. [ABSTRACT FROM AUTHOR]