New Triclinic Perovskite-Type Oxide Ba₅CaFe₄O₁₂ for Low-Temperature Operated Chemical Looping Air Separation

We present the discovery of Ba₅CaFe₄O₁₂, a new iron-based oxide with remarkable properties as a low-temperature driven oxygen storage material (OSM). OSMs, which exhibit selective and rapid oxygen intake and release capabilities, have attracted considerable attention in chemical looping technologies. Specifically, chemical looping air separation (CLAS) has the potential to revolutionize oxygen production as it is one of the most crucial industrial gases. However, the challenge lies in utilizing OSMs for energy-efficient CLAS at lower temperatures. Ba₅CaFe₄O₁₂, a cost-competitive material, possesses an unprecedented 5-fold perovskite-type A₅B₅O_15-δ structure, where both Fe and Ca occupy the B sites. This distinctive structure enables excellent oxygen intake/release properties below 400 °C. This oxide demonstrates the theoretical daily oxygen production rate of 2.41 m_O2³ kg_OSM^-1 at 370 °C, surpassing the performance of the previously reported material, Sr_0.76Ca_0.24FeO_3-δ (0.81 m_O2³ kg_OSM^-1 at 550 °C). This discovery holds great potential for reducing costs and enhancing the energy efficiency in CLAS.