Facile synthesis, characterization, mechanism and enhanced visible-light photocatalytic activity of SiW12/α-Fe2O3 nanocomposites

Abstract

A novel type of photocatalyst SiW₁₂/α-Fe₂O₃ created by combining SiW₁₂ NPs and α-Fe₂O₃ nanorings was synthesized through a “step by step” method. The structure, composition, morphology and the interaction between SiW₁₂ and α-Fe₂O₃ of the as-prepared composites are characterized by single crystal X-ray diffraction, FT-IR and UV spectroscopy, powder XRD, and SEM and XPS analyses. The results show that the SiW₁₂ unit exhibits a 3D zeolite-like open-framework structure with inter-crossing channels, and the α-Fe₂O₃ nanorings with an average size of about 150 nm are well dispersed on SiW₁₂ NPs. The UV-vis, photoluminescence and electrochemical impedance results suggest that SiW₁₂/3%α-Fe₂O₃ nanohybrid exhibits broad spectral absorption and excellent electron transfer capability. Fe₂O₃ and POM in the composition system can promptly transfer electrons, avoiding the recombination of electron–hole pairs and supplying more reaction active sites. Photocatalytic tests manifested that the composites exhibited excellent and stable activities towards the degradation of methylene blue (MB) under visible-light irradiation, and the SiW₁₂/3%α-Fe₂O₃ nanohybrid exhibited the best photocatalytic performance, which could reach 97.80% at pH = 6. The radical and hole trapping test results indicate that the hydroxyl radicals were identified as the main active species during the photodegradation process. Meanwhile, it is proved that the concentration of Cl⁻ in the solution has important influence on the photocatalytic performance of the composites. Also, the migration step of ˙O₂⁻ radicals to ˙OH radicals and the influence mechanism of chloride ions during the photocatalytic process have been studied. Finally, the probable photocatalytic mechanism was investigated systematically.