Design Principles of Perovskites for Thermochemical Oxygen Separation

Separation and concentration of O(2) from gas mixtures is central to several sustainable energy technologies, such as solar‐driven synthesis of liquid hydrocarbon fuels from CO(2), H(2)O, and concentrated sunlight. We introduce a rationale for designing metal oxide redox materials for oxygen separation through “thermochemical pumping” of O(2) against a pO(2) gradient with low‐grade process heat. Electronic structure calculations show that the activity of O vacancies in metal oxides pinpoints the ideal oxygen exchange capacity of perovskites. Thermogravimetric analysis and high‐temperature X‐ray diffraction for SrCoO(3−δ), BaCoO(3−δ) and BaMnO(3−δ) perovskites and Ag(2)O and Cu(2)O references confirm the predicted performance of SrCoO(3−δ), which surpasses the performance of state‐of‐the‐art Cu(2)O at these conditions with an oxygen exchange capacity of 44 mmol [Formula: see text] mol [Formula: see text] (−1) exchanged at 12.1 μmol [Formula: see text] min(−1) g(−1) at 600–900 K. The redox trends are understood due to lattice expansion and electronic charge transfer.