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 Fe₃O₄–TiO₂ exhibits a high degradation efficiency for RhB, and can be withdrawn from solution easily using an external magnetic field. (paper)