A New Nanocomposite Electrode Developed from Environmental Atmosphere Triggered Reconstruction for Efficient Reversible Protonic Ceramic Cells

Abstract Reversible protonic ceramic cells (r‐PCCs) are highly attractive energy storage and conversion technology, while the insufficient activity of state‐of‐the‐art air electrodes at reduced temperatures strongly limits their practical applications. Herein, this work reports a reduction/re‐oxidation strategy to design a new highly efficient, and durable nanocomposite air electrode for boosting the performance of r‐PCCs operated at intermediate temperatures. Specifically, single‐phase Ba(Co 0.4 Fe 0.4 Zr 0.1 Y 0.1 ) 0.9 Ni 0.1 O 3‐δ perovskite is selected as the precursor, its treatment in hydrogen atmosphere at 450 °C and then re‐oxidation in air leads to the formation of a nanocomposite, consisted of a perovskite‐based main phase and BaCoO 3‐δ and NiO secondary‐phase nanoparticles, where the BaCoO 3‐δ phase facilitates oxygen surface exchange while NiO nanoparticles promote surface oxygen/steam adsorption. The corresponding r‐PCC exhibits superior performance at 550 °C in a symmetrical cell (0.162 Ω cm 2 ), a single fuel cell (0.690 W cm −2 ) and an electrolysis cell (−1.066 A cm −2 at 1.3 V). Such nanocomposite is thermodynamically stable at intermediate temperatures and offers better thermomechanical compatibility with protonic electrolyte because of the reduced thermal expansion coefficient. As a result, superior durability in both fuel and electrolysis cell modes is demonstrated. This study paves a new way for designing outstanding air electrodes for r‐PCCs with great application potential.