Fe3O4/SiO2/CeO2 Core-Shell Magnetic Nanoparticles as Photocatalyst

The Fe3O4/CeO2 magnetic photocatalyst was prepared by coating directly onto the surface of magnetic Fe3O4 particles. However a direct contact of CeO2 onto the surface of magnetic Fe3O4 particles presented unfavorable heterojunction, thus the SiO2 barrier layer between magnetic Fe3O4 and CeO2 was prepared as a core-shell stucture to reduce the negative effect by combining three steps of the hydrothermal, sonochemical and homogeneous precipitation. The high resolution electron microscopy (HRTEM) confirmed that Fe3O4/SiO2/CeO2 core-shell magnetic nanoparticles exhibited core-shell structure including a magnetic Fe3O4 core, a SiO2 middle layer and CeO2 particle coating. The results of the photocatalytic activity revealed that the pseudo-first order rate constants for formic and oxalic acids degradation was increased in the following order: Fe3O4/SiO2/CeO2 core-shell magnetic nanoparticles> single-phase CeO2> Fe3O4/CeO2. SiO2 middle layer and their surface properties may cause the good photocatalytic activity of the Fe3O4/SiO2/CeO2 core-shell magnetic nanoparticles. The possible mechanism of the photoexcited electron-hole separation and transport processes was proposed based on the obtained morphology via HRTEM morphology and UV-Vis DRS results. The Fe3O4/SiO2/CeO2 core-shell magnetic nanoparticles were compared and recovered in the consecutive cycles of use by external magnetic field. The material showed good stability with regards to photocatalytic performance for three cycles of use.