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

A novel type of photocatalyst SiW 12 /α-Fe 2 O 3 created by combining SiW 12 NPs and α-Fe 2 O 3 nanorings was synthesized through a "step by step" method. The structure, composition, morphology and the interaction between SiW 12 and α-Fe 2 O 3 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 SiW 12 unit exhibits a 3D zeolite-like open-framework structure with inter-crossing channels, and the α-Fe 2 O 3 nanorings with an average size of about 150 nm are well dispersed on SiW 12 NPs. The UV-vis, photoluminescence and electrochemical impedance results suggest that SiW 12 /3%α-Fe 2 O 3 nanohybrid exhibits broad spectral absorption and excellent electron transfer capability. Fe 2 O 3 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 SiW 12 /3%α-Fe 2 O 3 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 &z.rad;O 2 − radicals to &z.rad;OH radicals and the influence mechanism of chloride ions during the photocatalytic process have been studied. Finally, the probable photocatalytic mechanism was investigated systematically. The photocatalytic mechanism of the SiW12/α-Fe2O3 nanohybrid.