Enhanced visible light photoelectrochemical water splitting using nanotubular FeOx-TiO2 annealed at different temperatures

Abstract

Nanostructured semiconductor photoelectrodes that can operate under renewable solar energy are of great interest for both fundamental studies and practical applications. In this paper, we studied the semiconducting and photoelectrochemical properties of nanotubular FeO x -TiO 2 annealed at different temperatures. Nanostructured anodic titanium oxide layers were modified by impregnation with a solution containing 100 mM FeCl 3 followed by their annealing at 400 °C, 500 °C, and 600 °C. The synthesized materials were characterized by using a field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy (RS), diffuse reflectance spectroscopy (DRS), electrochemical impedance spectroscopy (EIS), Mott-Schottky analysis, and photoelectrochemical measurements. It was found that depending on the annealing temperature, the studied materials showed a different photoelectrochemical response. The lowest value of band gap was observed for the sample annealed at 500 °C, which is related to the presence of a mixture of anatase and rutile phases together with iron oxides. • Three types of morphology were detected in the studied materials. • α-FeOOH, α-Fe 2 O 3 , γ-Fe 2 O 3 , Fe 3 O 4 and FeO were detected by Raman analyses. • The narrowest optical gap was observed for the FeO x -TiO 2 sample annealed at 500 °C. • Grain boundary passivation mechanism induced by introducing FeO x was observed.