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.