Spatially confined Fe2O3 in hierarchical SiO2@TiO2 hollow sphere exhibiting superior photocatalytic efficiency for degrading antibiotics

Although TiO2-based photocatalysts have achieved great successes for the degradation of organic pollutants, the complete removal of antibiotics is hard to be realized because of its unique macromolecular ring structure under solar-light irradiation. Herein, this work demonstrates the rational design of the hierarchical hollow SiO2-Fe2O3@TiO2 (SFT) photocatalyst by introducing spatially confined Fe2O3 as a modifier of TiO2, in which inner SiO2 serves as a carrier to support and disperse Fe2O3 in order to obtain small size of Fe2O3 (2–6 nm), while outer TiO2 acts as a bounding wall to protect Fe2O3 from aggregation and abscission. The as-synthesized SFT photocatalyst not only can overcome easy corrosion, dissolution and deactivation of Fe2O3 during the photoreaction process, but also can substantially enhance the adsorption of antibiotics because of its hierarchical hollow structure, facilitating the separation of electron-hole pairs and prolonging the trapping of incident light. Therefore, the SFT photocatalyst manifests the complete removal of antibiotics under simulated solar light irradiation. The intermediates of antibiotics were analyzed by liquid chromatography-mass spectrometry (LC/MS) and the possible degradation pathway was proposed accordingly. Besides, SFT photocatalyst exhibits an excellent recyclability due to confinement effect. Especially, the as-synthesized SFT also achieves the 100% degradation rate of antibiotics under natural sunlight irradiation, efficiently overcoming the incomplete removal of antibiotics for many previous TiO2-based photocatalysts.