One-pot derived thermodynamically quasi-stable triple conducting nanocomposite as robust bifunctional air electrode for reversible protonic ceramic cells

Reversible protonic ceramic cell (RePCC) is an efficient, scalable, and fuel-flexible energy conversion and storage technology. However, finding single-phase triple conducting (H⁺/O^2-/e^-) electrodes with high electrochemical activity, structural and thermomechanical stability still faces great challenges. Herein, we propose a thermodynamically quasi-stable triple conducting perovskite-perovskite nanocomposite as bifunctional RePCC air electrode with exceptional performance, which is composed of a Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ-based mixed oxygen ion and electronic conductor and a BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-δ-based protonic conductor and synthesized through one-pot method. Some unique structure introduces increased number of active sites and rich two-phase boundary, and tailored two phase composition, which contributes to the superior performance for both oxygen reduction and evolution reactions. In addition, the intimate connection of the two phases, their cation interexchange characteristics and the thermodynamically quasi-stable composition in the nanocomposite brings the electrode matchable thermal compatibility to the electrolyte and high structural stability that accounts for the superior durability.