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-delta is reported, which is self-configured into a composite of Pr4Ni1.8Co1.2O10-delta (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 Omega cm(2) at 600 degrees 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 degrees 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.