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 CO2, H2O, 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 SrCoO3-, BaCoO3- and BaMnO3- perovskites and Ag2O and Cu2O references confirm the predicted performance of SrCoO3-, which surpasses the performance of state-of-the-art Cu2O at these conditions with an oxygen exchange capacity of 44mmolO2molSrCoO3-(-1) exchanged at 12.1molO2min(-1)g(-1) at 600-900K. The redox trends are understood due to lattice expansion and electronic charge transfer.