Spinel-type ferrite nanoparticles: Synthesis by the oil-in-water microemulsion reaction method and photocatalytic water-splitting evaluation

Cobalt, nickel and zinc nanosized spinel-type ferrites (MFe 2 O 4, M: Co 2+, Ni 2+ and Zn 2+ ) were synthesized by the novel oil-in-water microemulsion method. These compounds have not been fully studied for H 2 production by the water-splitting reaction, especially those prepared by microemulsion. Through proper characterization, features like crystal structure, efficient visible light absorption, high-sorption capacity and adequate textural properties, were demonstrated for thermal treated Co, Ni and Zn microemulsion synthesized nanoferrites. These characteristics favored the visible light-driven H 2 production (monitored by gas chromatography) of MFe 2 O 4 nanoparticles dispersed in water (2% MeOH), under experimental conditions. Particularly, ZnFe 2 O 4 yielded a higher amount of H 2 (354 μmolH 2 g −1 ) compared to Co (128 μmolH 2 g −1 ) and Ni (129 μmolH 2 g −1 ) ferrites in an 8 h experiment, presumably due to more favorable electronic band positions. This work represents a new contribution to the hydrogen evolution studies using ferrite nanoparticles.