Fast redox kinetics in SrCo1-xSbxO3-δ perovskites for thermochemical energy storage and oxygen separation

Abstract

The use of perovskite materials for thermochemical energy storage and oxygen separation has been gaining momentum in recent years due to their ability to topotactically exchange large volumes of oxygen, and their chemical and structural flexibility. B-site substituted SrCoO3-δ derivatives have previously been investigated as promising materials for intermediate temperature solid oxide fuel cell cathodes due to the stabilization of a 3 C perovskite structure with high electronic and ionic conductivity that allows large oxygen storage capabilities. Here, antimony-substituted strontium cobalt oxides are investigated and identified as new candidate materials for thermochemical oxygen separation applications. In this work we shed light on the exceptional redox kinetics and cyclability of antimony-substituted variants undergoing oxygen exchange at intermediate temperatures (500 to 800 °C). Through the use of density functional theory and isothermal gas atmosphere switching, we demonstrate how the inductive effect of the more electronegative antimony dopants in the Co position, facilitates the kinetics of metal oxide oxidation, whilst hindering reduction reactions. SrCo0.95Sb0.05O3−δ was identified to isothermally evolve 3.76 cm3 g−1 of oxygen at 500 °C and calculated to produce up to 10.44 cm3 g−1 under temperature-swing reaction configurations aligning with previously reported materials.