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Redox Behavior of Solid Solutions in the SrFe 1‐x Cu x O 3‐δ System for Application in Thermochemical Oxygen Storage and Air Separation
Author(s) -
Vieten Josua,
Bulfin Brendan,
Starr David E.,
Hariki Atsushi,
de Groot Frank M. F.,
Azarpira Anahita,
Zachäus Carolin,
Hävecker Michael,
Skorupska Katarzyna,
Knoblauch Nicole,
Schmücker Martin,
Roeb Martin,
Sattler Christian
Publication year - 2019
Publication title -
energy technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.91
H-Index - 44
eISSN - 2194-4296
pISSN - 2194-4288
DOI - 10.1002/ente.201800554
Subject(s) - thermogravimetric analysis , oxygen storage , redox , x ray photoelectron spectroscopy , stoichiometry , oxygen , perovskite (structure) , analytical chemistry (journal) , materials science , x ray absorption spectroscopy , chemistry , inorganic chemistry , absorption spectroscopy , crystallography , chemical engineering , engineering , physics , quantum mechanics , organic chemistry , chromatography
Perovskite oxides with temperature and oxygen partial pressure dependent non‐stoichiometry δ , such as SrFeO 3‐δ or its Cu‐doped 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 SrFe 1‐x Cu x O 3‐δ 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 SrFe 1‐x Cu x O 3‐δ , revealing very high reaction speeds with t 1/2 =13 min at 150 °C for SrFeO 3‐δ . Our results indicate that SrFe 1‐x Cu x O 3‐δ solid solutions can be applied for oxygen storage and air separation with high capacity at relatively low temperatures, which allows an efficient thermochemical process.