An Active and Robust Air Electrode for Reversible Protonic Ceramic Electrochemical Cells

Reversible protonic ceramic electrochemical cells (R-PCECs) are a promising option for efficient and low-cost generation of electricity and hydrogen. Commercialization of R-PCECs, however, hinges on the development of highly active and robust air electrodes. Here, we report an air electrode consisting of PrBa0.8Ca0.2Co2O5+δ and in situ exsolved BaCoO3−δ nanoparticles (PBCC–BCO) that shows minimal polarization resistance (∼0.24 Ω cm2 at 600 °C) and high stability when exposed to humidified air with 3−50% H2O. An R-PCEC utilizing PBCC-BCO demonstrates remarkable performances at 600 °C: achieving a peak power density of 1.06 W cm–2 in the fuel cell mode and a current density of 1.51 A cm–2 at 1.3 V in an electrolysis mode. More importantly, the R-PCECs demonstrate an exceptionally high durability over 1833 h of continuous operation in the electrolysis mode. This work offers an efficient approach to design of high-performance and durable electrodes for R-PCECs.