A Highly Active and Robust Air Electrode for Reversible Protonic Ceramic Cells: Advanced Performance Achieved by Low-Lewis-Acid-Strength Cation Doping Strategy

Reversible protonic ceramic cells (RPCCs) are highly regarded as advancing energy conversion devices with broad application prospects in electricity supply and power integration. However, the performance of the air electrode remains a critical challenge for RPCC technology. In this study, a highly active and robust air electrode catalyst Ba0.95K0.05Co0.2Zn0.2Ga0.2Zr0.2Y0.2O3−δ (BKCX) is explored based on the high-entropy design and low-Lewis-acid-strength cation (K+) doping. The high-entropy structure ensures the thermodynamic stability of the air electrode. The doping of low-Lewis-acid-strength cation (K+) facilitates the steam adsorption and the protonation processes. At 700 °C, RPCC with BKCX air electrode demonstrates a peak power density of 1.33 W cm–2 in the fuel cell mode and an electrolytic current density of 2.81 A cm–2 at 1.3 V in the electrolysis cell mode. The RPCC maintains efficient operation reversely for hundreds of hours without observable performance degradation and structural collapse.