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A paramagnetic-ferromagnetic transition was observed in normal spinel zinc ferrite (ZnFe 2 O 4 ) during atomic hydrogenation at room temperature. Magnetic measurements showed enhanced ferromagnetic property with increasing hydrogenation time. The hydrogenated ZnFe 2 O 4 has normal spinel structure according to X-ray diffraction (XRD) and Raman analyses. Iron hydride was found from the XRD and X-ray absorption fine structure results. No A–B site ions exchange was observed in the x-ray absorption spectra while the atomic distances of Fe–O, Zn–O, Fe–Fe, Zn–Zn and Fe–Zn coordinations were reduced. A hybrid of Fe 2+ and Fe 3+ in hydrogenated ZnFe 2 O 4 can be further revealed through deconvolution of x-ray absorption near edge structure. The paramagnetic-ferromagnetic transition and enhanced ferromagnetic property were mainly due to the formation of iron hydride and the B-site super-exchange interactions of Fe 2+ and Fe 3+ . [ABSTRACT FROM AUTHOR]

The environmental-friendly hematite iron oxide (α-FeO) has important application prospects in the photocatalysis field owing to its narrow indirect band gap. Here, we report a band gap engineering of α-FeO by incorporation of electrochemically-generated atomic hydrogen at moderate conditions. The ultraviolet-visible spectra show the reduction of the α-FeO band gap after hydrogenation and the absorption region from 200-800 nm is enhanced, especially in the visible light region. First principles calculation reveals the mixing of the new hybrid energy level with the valence band top resulting in a decrease in the band gap of α-FeO. Further photocatalytic degradation experiments of dyes demonstrate that the photocatalytic efficiency of α-FeO can be greatly enhanced by the atomic hydrogen incorporation. The hydrogenated α-FeO can be easily recycled by magnets and has good photocatalytic stability. These findings offer possibilities for utilizing this inexpensive and earth-abundant oxide materials in the pollution controlling areas. [ABSTRACT FROM AUTHOR]