Visible-light-active novel α-Fe₂O₃/Ta₃N₅ photocatalyst designed by band-edge tuning and interfacial charge transfer for effective treatment of hazardous pollutants

Novel α-Fe₂O₃/Ta₃N₅ nanocomposites were designed based on the Z-scheme system and a suitable band-edge potential for photocatalytic action. The combination of α-Fe₂O₃ and Ta₃N₅ showed substantially higher photocatalytic activity compared with α-Fe₂O₃ or Ta₃N₅ alone. The improved performance was attributed to (i) efficient electron–hole separation at the interface between α-Fe₂O₃ and Ta₃N₅, which resulted in high light absorption; and (ii) a favorable band-edge position to generate reactive oxygen species. The nanocomposites were prepared by precipitation techniques and annealing at different temperatures in a sealed chamber. The photocatalytic activity of the samples in methylene blue degradation under visible light (VL) was monitored for 60 min. The best result of 98.26% was obtained for the FTN-1 nanocomposite (annealed at 450 ℃), which is attributed to its high surface area, small particle size, and small crystallite size. Under similar conditions, FTN-1 exhibited 83.73%, 94.19%, and 48.86% efficiency in degrading rhodamine 6 G, non-photosensitizing Congo red, and the colorless contaminant phenol. The rate of MB degradation by FTN-1 was 539.4% and 651.2% greater than the rates of MB degradation by single catalysts α-Fe₂O₃ and Ta₃N₅, respectively. These values increased to 1939.4% and 2341.5% at pH 12 and a degradation time of 15 min. No substantial loss of activity or structural composition was observed after five consecutive runs. Overall, the nanocomposites exhibited a wide range of VL absorption and high photocatalytic efficiency. These results shed new light on the VL-active, Z-scheme photocatalyst field and indicate that the proposed photocatalysts are suitable for practical wastewater treatment.