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Abstarct Ferrous titanate (FeTiO3) nanoparticles with hexagonal disc structure were prepared by a simple hydrothermal method. The VSM results show that ferromagnetic-paramagnetic transition of FeTiO3 caused by high temperature hydrogenation. The morphology and lattice structure of FeTiO3 was characterized in detail by XRD, Raman, SEM and TEM. It was found that the magnetic transition of FeTiO3 nanoparticles after hydrogenation could be attributed to the change of lattice structure and surface effect. Further research by XPS found that the high temperature hydrogenation treatment could cause the change of elemental valence states and oxygen vacancies concentration for FeTiO3. The weakening of double exchange interaction (Fe2+-O-Fe3+) and the reduction of uncompensated surface spin were the main cause of the ferromagnetic-paramagnetic transition. This experiment would provide a new idea for regulating the magnetic property of materials.

A novel hydrogenated LaFeO3 was fabricated and firstly used as photocatalyst in the application of visible-light photocatalytic decomposition of organic contaminant. Through the adjusting of annealing atmosphere and temperature, a series of treated LaFeO3 with oxygen vacancies were obtained. Compared with untreated LaFeO3 and argon treated LaFeO3, hydrogenated LaFeO3 photocatalysts exhibited higher catalytic ability. This notably improved catalytic ability was mainly assigned to the formation of disordered layer on the surface of hydrogenated LaFeO3. The surface oxygen vacancies of LaFeO3 caused by hydrogenation were beneficial to light absorption and separation of photogenerated carriers. In this system, we found the amount of surface oxygen vacancies had a direct impact on the catalyst ability of hydrogenated LaFeO3 photocatalysts. In addition, the magnetic hydrogenated LaFeO3 photocatalysts were stable, and reused after five times without obvious decrease of catalytic ability.

This paper firstly studied an obvious magnetic transformation from paramagnetism to superparamagnetism in hydrogenated ZnFe2O4 nanoparticles. The zinc ferrite nanoparticles were successfully prepared by a simple solid-state reaction followed by a ball milling method. Moderate thermal treatments under hydrogen atmosphere were carried out, and a phenomenon was observed that the magnetic behavior of zinc ferrite nanoparticles transformed from paramagnetism to superparamagnetism. Various characterizations were carried out to confirm the creation of the hydrogen doping induced defects under post-treatments, which may be crucial for the magnetic transformation. By studying the effect of the defects caused by hydrogenation on the magnetization, we found that the oxygen vacancies could alter the magnetic ordering of materials and therefore modulate the magnetic behaviors. In addition, the saturation magnetization decreased after reheating the hydrogenated Zn-ferrite samples in the air, which indicated that the oxygen vacancies and Fe2+ ions directly modulated the magnetization of the Zn-ferrite materials. Notably, the residual saturation magnetization was still higher than raw Zn-ferrite, indicating that the changes of cation distribution could also modulate the magnetization and certain changes were irreversible.