An Active and Durable Misfit-Layered Air Electrode for Reversible Protonic Ceramic Electrochemical Cells

Developing air electrode materials with high catalytic activity and durability of oxygen reduction/evolution reactions is an important solution to address the performance and stability problems of reversible protonic ceramic electrochemical cells (R-PCECs). This work reports an active and durable misfit-layered air electrode with a chemical formula of Ca₃Co_3.8Mo_0.2O_9+δ. A low area-specific resistance of 0.13 Ω cm² with reasonable operation stability over 100 h is achieved in the air with 30% steam at 650 °C, likely attributed to the fast surface exchange kinetics and bulk diffusion processes. A single cell with this electrode demonstrates outstanding performance in fuel cell and electrolysis modes, with a peak power density of 1.62 W cm^–2 and an electrolysis current density of −2.98 A cm^–2 at 650 °C. Most notably, Mo ions doped in air electrodes significantly enhance the cell’s operational reversibility stability, with no observed performance degradation after 52 reversible cycles and over 200 h in dual modes of fuel and electrolysis cell tests.