Facile synthesis of novel Fe3O4@SiO2@mSiO2@TiO2 core-shell microspheres with mesoporous structure and their photocatalytic performance

Abstract

Novel Fe3O4@SiO2@mSiO2@TiO2 (mSiO2: mesoporous SiO2) core-shell microspheres were fabricated by a facile method. The obtained materials were characterized by X-ray diffraction (XRD), Raman spectra, N2 adsorption-desorption, scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM). The results revealed that the as-prepared microspheres have a good monodispersity, high magnetization and uniform core-shell structure with amorphous and mesoporous SiO2 coatings. The photocatalytic activity was evaluated on photodegradation of Methylene blue (MB) under UV-light irradiation. The results indicated that the novel material had the stronger photoactivity than Degussa P25. The superior photocatalytic property of Fe3O4@SiO2@mSiO2@TiO2 is mainly attributed to the positive effect of three components including Fe3O4 core, mesoporous SiO2 intermediate layer and TiO2 particles, due to the high surface area and the reduced recombination probability of photogenerated electrons/holes. The degradation of MB by these catalysts follows the pseudo-first-order kinetic model and Fe3O4@SiO2@mSiO2@TiO2(2.5) was found to be the best. Moreover, the Fe3O4@SiO2@mSiO2@TiO2 could be easily separated by an external magnet, and the recovered catalyst can be reused five times without any significant loss of photocatalytic activity. The results manifest that the well-designed Fe3O4@SiO2@mSiO2@TiO2 is a promising candidate in wastewater treatment application.