Enhanced oxygen-release/storage properties of Pd-loaded Sr₃Fe₂O_7-δ

This study proves that a small amount of Pd loading (1 wt%) on Sr₃Fe₂O_7-δ can dramatically enhance the oxygen-storage properties of Sr₃Fe₂O_7-δ. The topotactic oxygen intake and release between Sr₃Fe₂O_6.75 and Sr₃Fe₂O₆ takes place in response to gas switching between an O₂ flow and H₂ flow, regardless of the presence or absence of Pd loading. The effect of Pd loading is significant for the oxygen-release process under H₂ atmosphere; that is, highly dispersed Pd metal nanoparticles sized less than 1 nm formed on Pd/Sr₃Fe₂O_7-δ to promote H₂ dissociation, resulting in the improvement of the oxygen-release temperature and rate. Pd/Sr₃Fe₂O_7-δ with a layered perovskite structure has a higher oxygen-release property at lower temperature than Pd/SrFeO_3-δ with a perovskite phase without the layered structure. These facts indicate that the surface reaction as well as the crystal structure are responsible for the oxide ion mobility in perovskite structure, and also provide guidelines for designing novel oxygen-storage materials.