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

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 Pr2Ni0.6Co0.4O4‐δ is reported, which is self‐configured into a composite of Pr4Ni1.8Co1.2O10‐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. A self‐configured composite of Ruddlesden‐Popper perovskite Pr4Ni1.8Co1.2O10−δ and Pr6O11 is developed as the air electrode for reversible protonic ceramic electrochemical cells. The composite electrodes show decent electrochemical activity after being treated in wet air and favorable operational durability.