In this study, the STF x photocatalyst powder was synthesized with a high temperature solid state reaction. The microstructures and surface of samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The electronic properties and local structure of the perovskite STF x (0 ≤ x ≤ 1) systems were probed by extended X-ray absorption fine structure (EXAFS) spectroscopy. The XPS results revealed that with increasing iron doping, the amount of Fe3+ and Fe4+ increased significantly. The X-ray absorption data are discussed in detail with respect to the Fe (Ti) K-edge. The substitution of iron by titanium increased the Ti (Fe)–O first shell disorder factors that can be explained by increasing the oxygen vacancies. Oxygen vacancies or defects act as electron traps, which could capture the photo induced electrons and thus could effectively inhibit the recombination of the photo induced electrons and holes. Moreover due to the substitution of Ti with Fe, lattice shrinkage was observed and the largest derivation from the Gaussian distribution in STF x was from those samples with x = 0.6 and x = 0.8. The substitution of iron by titanium increased the iron valence state, hence the formation of the Jahn–Teller Fe4+ ion. With increasing iron dopant the [Ti(Fe)–O]ave decreased and bond length of [Ti–O] and the consequent [Ti–O–Ti] increased and this phenomenon affected the photocatalyst and photo degradation properties of material and also decreased its efficiency.
Graphical abstract Highlights
► STF x catalyst prepared by a high temperature solid state reaction process. ► The electronic properties and local structure have been probed by EXAFS spectroscopy. ► The substitution of iron increases iron valence state and the Jahn–Teller ion formed. ► The Fe4+ ion causes disorder in the first shell and increases the oxygen vacancy defect. ► Iron doping led to decreasing of [Ti(Fe)–O]ave and increasing the photocatalyst property.
M. Ghaffari, T. Liu, H. Huang, O.K. Tan, M. Shannon
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