High-temperature water oxidation activity of a perovskite-based nanocomposite towards application as air electrode in reversible protonic ceramic cells

Reversible protonic ceramic cells (r-PCCs) can operate alternately in fuel cell and electrolysis cell modes, while their practical applications are limited due to the lack of air electrodes with high oxygen reduction/evolution reaction (ORR/OER) activities. A nanocomposite Ba0.95(Co0.4Fe0.4Zr0.1Y0.1)0.95Ni0.05O3-δ (BCFZYN), consisting of a major perovskite phase (D-BCFZYN) and a minor NiO phase, has demonstrated outstanding ORR activity in protonic ceramic fuel cells [1]. Herein, we experimentally and theoretically demonstrate that BCFZYN possesses excellent OER activity. Density functional theory calculations indicate that NiO nanoparticles enhance water adsorption while D-BCFZYN accelerates oxygen desorption and proton conduction, thus promoting OER kinetics. A cell with BCFZYN air electrode achieved a current density of − 1267 mA cm-2 at 1.3 V at 600 oC, while maintaining favorable durability of 372 h. The corresponding cell demonstrated stable operation during cycling mode between fuel cell and electrolysis modes, suggesting the material has great potential as an air electrode for r-PCCs.