A Universal Oxygen-Electrode for Reversible Solid Oxide Electrochemical Cells at Reduced Temperatures

Solid oxide electrochemical cells (SOCs) are promising energy storage and conversion devices that represent a facile and sustainable route for converting chemical fuels into electricity and vice versa on demand. In particular, the discovery of an oxygen-electrode material that exhibits excellent reactivity and durability, is the key to related device technology. Here, we present Ta-doped BaCoO3-δ catalysts that exhibit record-breaking electrode performance in both fuel cell and electrolysis operations, which were demonstrated with two types of SOCs using oxygen ion- and proton-conducting electrolytes. The introduction of pentavalent Ta ions allows the parent oxide to maintain a cubic perovskite structure with high symmetry, which substantially improves its phase stability, electronic and ionic conductivity, and even catalytic activity for oxygen reduction and evolution. Hence an assortment of best-performing fuel cell and electrolysis cell results are recorded; for example, a proton-conducting SOC conveying a peak power density of 2.26 W cm-2 at 650oC. The design principle of the versatile electrode presented in this study not only allows for the realization of high-performance SOCs, but also contributes to a broader-real world impact: a multipurpose, standardized electrode of high demand will result in significant cost reductions for related electrochemical devices.