Understanding of A-site deficiency in layered perovskites: promotion of dual reaction kinetics for water oxidation and oxygen reduction in protonic ceramic electrochemical cells

Protonic ceramic electrochemical cells (PCECs) are promising solid-state energy conversion devices which enable the conversion of energy between electricity and hydrogen at intermediate temperatures. Rapid conversion between chemical and electrical energy via PCEC technology will assist in overcoming grand challenges in energy storage. To achieve highly efficient reversible operation between hydrogen production and electricity generation, boosting water-oxidation and oxygen reduction activities of the oxygen electrode while maintaining the durable operation is one of the early-stage technical opportunities. In this study, an A-site deficient layered perovskite (PrBa0.8Ca0.2)0.95Co2O6−δ has been developed as an oxygen electrode for a PCEC which presents superior electrochemical performances. The electrolysis current density reached as high as −0.72 A cm−2 at 1.3 V, and a peak power density of 0.540 W cm−2 was obtained at 600 °C in electrolysis and fuel cell mode, respectively. The PCEC with the new electrode shows good durability under practical operating conditions for 160 hours in both operating modes with no observable degradation. The reversibility between the electrolysis and fuel cell mode is also successfully demonstrated.