Self‐Configured Composites of Ruddlesden‐Popper Perovskite and Pr₆O₁₁ as Efficient and Durable Air Electrodes for Reversible Protonic Ceramic Electrochemical Cells

Abstract A breakthrough in the development of air electrodes is critical to minimizing the performance deterioration of reversible protonic ceramic electrochemical cells (R‐PCECs), which have demonstrated the potential to be the most promising electrochemical device for energy storage and conversion. Here, a Co‐doped Ruddlesden‐Popper (RP) perovskite with a nominal formula of Pr₂Ni_0.6Co_0.4O_4‐δ is reported, which is self‐configured into a composite of Pr₄Ni_1.8Co_1.2O_10‐δ (PNCO, 89.57 wt.%) and Pr₆O₁₁ (10.43 wt.%), suggested by the X‐ray diffraction refinement. The composite electrodes exhibit improved electrochemical activity with an area‐specific resistance of 0.33 Ω cm² at 600 °C after being treated with wet air, due primarily to the raised surface exchange, bulk diffusion capabilities, and the increasing amount of Pr₆O₁₁ with catalytic activity. The R‐PCECs with the composite electrodes achieve a maximum power density of 1.32 W cm⁻² and a current density of 3.09 A cm⁻² at 1.3 V with acceptable Faradaic efficiencies at 650 °C. Furthermore, the composite electrodes show benign operational durability in fuel cell mode (‐0.5 A cm⁻² for 167 h) and electrolysis mode (+0.5 A cm⁻² for 176 h), and promising cycling stability (+/‐0.5 A cm⁻²) of 124 h at an interval of 2 h.