Regulation of Ni/Co Ratio and Gas Transport in High‐Order Ruddlesden–Popper Perovskite Air Electrodes for Protonic Ceramic Electrochemical Cells

Abstract The delicate design of efficient air electrodes is conducive to improving the reaction kinetics and operational durability of protonic ceramic electrochemical cells (PCECs) at intermediate‐low temperatures. Here, a series of high‐order Ruddlesden–Popper (RP) perovskite electrodes are developed via the regulation of Ni/Co ratio and porosity for efficient charge/gas transfer. As verified by structural analysis and electrochemical characterizations, the electrode with a composition of Pr 4 Ni 1.8 Co 1.2 O 10‐δ (PNCO64) shows the most matchable thermal expansion behavior with electrolytes, and highest electrical conductivity, and best catalytic activity toward oxygen reduction/evolution reactions. The Ni/Co ratio of 6:4 can induce the formation of an optimized amount of Pr 6 O 11 in PNCO64, which is likely the pivotal source of the improved catalytic activity. When implemented on PCECs, the PNCO64 electrodes with the addition of 5% graphite pore‐former achieve a remarkable peak power density (1.18 W cm −2 ) and a high current density of 2.08 A cm −2 at 1.3 V at 600 °C. Excellent durability in fuel cell mode (≈85 h) and electrolysis mode (≈92 h) is also accomplished in PCECs at 600 °C.