Activating molecular oxygen by a defect-engineered S-scheme α-Fe₂O₃/g-C₃N₅ heterojunction for efficient in-situ...

Solar-driven molecular oxygen activation provides a sustainable strategy for generating reactive oxygen species, but the crucial step of effective electron transfer from the active sites to activate molecular oxygen remains challenging. Herein, a defect-engineered S-scheme α-Fe₂O₃/g-C₃N₅ heterojunction is meticulously constructed to facilitate molecular oxygen activation through the precise orientation of photoelectron transfer channels. Such a special transfer path establishes an effective consecutive photoelectron transfer channel between g-C₃N₅ and α-Fe₂O₃. Nitrogen defect introduction synergizes with the built-in electric field to enhance carrier separation and indirectly facilitate molecular oxygen activation. Therefore, the optimized α-Fe₂O₃/g-C₃N₅ heterojunction exhibited excellent in-situ photo-Fenton degradation activity, and the degradation rate for tetracycline was 1.61 and 4.78 times higher than g-C₃N₅ and α-Fe₂O₃, respectively. Detailed in-situ irradiated X-ray photoelectron spectroscopy, femtosecond transient absorption spectroscopy, and density functional theory calculations elucidate the interfacial charge transfer mechanisms within the S-scheme α-Fe₂O₃/g-C₃N₅ heterojunction. Moreover, in-situ diffuse reflectance infrared fourier transform spectroscopy further corroborated the mechanism of activating molecular oxygen in α-Fe₂O₃/g-C₃N₅. This research provides insight into constructing efficient heterojunction photocatalysts for orienting molecular oxygen activation and achieving outstanding in-situ photo-Fenton catalytic performance.