Redox Behavior of Solid Solutions in the SrFe1 xCuxO3 delta System for Application in Thermochemical Oxygen Storage and Air Separation

Perovskite oxides with temperature and oxygen partial pressure dependent non stoichiometry amp; 948;, such as SrFeO3 amp; 948; or its Cudoped variants, can be applied as redox materials for two step thermochemical processes, i.e. to reversibly store oxygen and thereby thermal energy, or separate air using concentrated solar power. We studied the redox state of Cu in SrFe1 xCuxO3 amp; 948; samples using in situ X ray photoelectron spectroscopy XPS and X ray absorption XAS measurements in oxygen atmospheres using synchrotron radiation, and characterized these materials through thermogravimetric analysis. By this means, we show how spectroscopic and thermogravimetric data are correlated, suggesting that Cu and Fe are reduced simultaneously for x 0.05, whereas the reduction of samples with x 0.15 is mainly driven by a change in the Fe oxidation state. Furthermore, we studied the re oxidation kinetics of reduced SrFe1 xCuxO3 amp; 948;, revealing very high reaction speeds with t1 2 13 min at 150 C for SrFeO3 amp; 948;. Our results indicate that SrFe1 xCuxO3 amp; 948; solid solutions can be applied for oxygen storage and air separation with high capacity at relatively low temperatures, which allows an efficient thermochemical proces