Bio-templated synthesis of Fe3O4–TiO2 composites derived from Chlorella pyrenoidosa with enhanced visible-light photocatalytic performance

A series of Fe3O4–TiO2 composites were successfully synthesized using Chlorella pyrenoidosa as a bio-template. C. pyrenoidosa is not only a promising bio-template for obtaining Fe3O4 and TiO2 nanoparticles (NPs) but is also a natural dye sensitizer source that improves the photocatalytic activity of the TiO2 NPs under visible light. The bandgap energy of Fe3O4–TiO2 is narrower than that of TiO2 due to the coupling between the Fe3O4 and TiO2 NPs. The coupling and dye-sensitization lead to the rapid separation and suppressed recombination of electron-hole pairs in Fe3O4–TiO2, which enhances the photocatalytic activity of TiO2 under visible light. The photocatalytic activity of the as-prepared composites was evaluated by degrading a rhodamine B (RhB) aqueous solution under visible-light irradiation. Fe3O4–TiO2 exhibits a high degradation efficiency for RhB, and can be withdrawn from solution easily using an external magnetic field.