Oxygen electrodes for protonic ceramic cells

Protonic ceramic cells (PCCs), including protonic ceramic fuel cells (PCFCs) and electrolysis cells (PCECs), are attracting increasing attention owing to several advantages such as their low activation energy for proton diffusion, fuel flexibility, absence of fuel dilution, and potentially lower housing/stacking costs at intermediate operating temperatures (400–600 °C). However, one of the major challenges for PCCs is the design and realization of oxygen electrodes for efficient oxygen reduction and water splitting reactions. Many research groups have devoted efforts to this research topic and have obtained encouraging results showing improved power output and current density in PCCs owing to the improvement of the oxygen electrode. This trend needs to be continued to enable the commercialization of the PCC technology. This review article describes the research progress in oxygen electrodes for PCCs, comprehensively summarizing literature work and offering prospective pathways for further development of high-performance oxygen electrodes.