Fabrication of Fe3O4/ZnO magnetite core shell and its application in photocatalysis using sunlight

Three chore-shell magnetite ZnO catalysts (Fe3O4/ZnO: M1, Fe3O4/SiO2/ZnO: M2, Fe3O4/SiO2-APTS/ZnO: M3) were prepared, characterized and tested for their photocatalysis in the degradation of methylene blue (MB) dye under sunlight irradiation. M2 and M3 catalysts exhibited better kinetics and higher activity. The silica coating of Fe3O4 in M2 and M3 catalysts enhanced efficient transport of MB dye to the ZnO site and thus enhanced photocatalysis. Photocatalytic reactivity was also related to the defects present in the samples under the synthesized conditions. Photoluminescence studies indicated the order of the defects in ZnO catalyst as M2 > M3 > M1. The presence of ZnO defects in the samples (M2 & M3) slowed electron recombination time, enhanced hydroxyl radical formation and hence performed faster degradation of MB. The significant enhancement in photoactivity could be attributed to the synergistic effect of adsorption by silica and ZnO catalysis. The recycle experiments using external magnetic showed the remained activity which demonstrated the stable and efficient magnetic separable catalysts.