Improved photochemical properties of Aurivillius Bi5Ti3FeO15 with partial substitution of Ti4+ with Fe3+

Abstract This work improved the optical absorption and photocatalytic ability of four-layered Aurivillius Bi5Ti3FeO15 through microstructural modification via partial substitution of Ti4+ with Fe3+. Bi5Ti3−xFe1+xO15 (x = 0–0.6) photocatalysts were prepared through sol-gel citrate-complexation synthesis. The sample crystallized into plate-like nanoparticles with [001] facets. Phase formation and crystal structure were confirmed via X-ray powder diffraction (XRD) Rietveld refinements. Bi5Ti3−xFe1+xO15 (x = 0–0.6) maintained its structural characteristic, i.e., a perovskite unit of (Bi3Ti3−xFe1+xO13)2– sandwiched by two (Bi2O2)2+ layers along c axis. The samples were investigated via scanning electron microscope (SEM), transmission electron microscope (TEM), energy-dispersive X-ray spectroscopy (EDX), and specific surface area analyses. The band gap showed characteristic transitions from the valence band (VB) of (O2p+Fet2 g+Bi6s) to the conduction band (CB) of (Ti-3d+Fe-eg). With increasing substitution of Ti4+ with Fe3+, the sample greatly red shifted its absorption edges. The d–d transitions in FeO6 greatly contribute to the narrow band-gap. Aurivillius is a potential photocatalyst and demonstrated photodegradation of Rhodamine B (RhB) under visible light irradiation (λ > 420 nm). Such photocatalytic activities were attributed to the special structural layer and the catalytic mediators of multivalent Ti4+/3+ and Fe3+/2+ ions in the perovskite slabs as confirmed by XPS measurements. Results suggested that substitution of Ti4+ with Fe3+ in an Aurivillius phase was an efficient method to modify the bandwidth and structure of Aurivillius phase. This phenomenon can be used as a strategy to improve the photochemical properties of Ti/Fe-containing Aurivillius phases.