Enhanced Photo-Fenton Activity of SnO₂/α-Fe₂O₃ Composites Prepared by a Two-Step Solvothermal Method

The x-SnO₂/α-Fe₂O₃ (x = 0.04, 0.07, and 0.1) heterogeneous composites were successfully prepared via a two-step solvothermal method. These composites were systematically characterized by the X-ray diffraction technique, field emission scanning electron microscopy, an energy dispersive spectrometer, X-ray photoelectron spectroscopy and a UV-visible spectrometer. It was found that SnO₂ nanoparticles were uniformly decorated on the surface of α-Fe₂O₃ particles in these heterogeneous composites. A comparative study of methylene blue (MB) photodegradation by α-Fe₂O₃ and x-SnO₂/α-Fe₂O₃ composites was carried out. All x-SnO₂/α-Fe₂O₃ composites showed higher MB photodegradation efficiency than α-Fe₂O₃. When x = 0.07, the MB photodegradation efficiency can reach 97% in 60 min. Meanwhile, the first-order kinetic studies demonstrated that the optimal rate constant of 0.07-SnO₂/α-Fe₂O₃ composite was 0.0537 min^-1, while that of pure α-Fe₂O₃ was only 0.0191 min^-1. The catalytic mechanism of MB photodegradation by SnO₂/α-Fe₂O₃ was examined. The SnO₂ can act as a sink and help the effective transfer of photo-generated electrons for decomposing hydrogen peroxide (H₂O₂) into active radicals. This work can provide a new insight into the catalytic mechanism of the photo-Fenton process.