Pivotal roles in advancing perovskite air electrodes for protonic ceramic cells - Research progress and perspectives

Protonic ceramic cells (PCCs), comprising protonic ceramic fuel cells (PCFCs) and protonic ceramic electrolysis cells (PCECs), are increasingly viewed as a promising route for high‐efficiency and low‐emission energy conversion. However, the advancement of PCCs has been hindered by the sluggish kinetics and inadequate stability of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at the air electrode. Notably, air electrode materials exhibiting durable triple (H + /e - /O 2- ) conductivity are anticipated to facilitate faster reaction kinetics and improve the stability of catalytic processes. Even with the substantial progress made so far, the development of air-electrode materials with superior performance still confronts substantial challenges. This review comprehensively summarizes recent advances in perovskite-based air electrodes for PCCs, encompassing fundamental mechanisms, the design of advanced materials, and performance modulation strategies. Special emphasis is placed on degradation mechanisms and performance enhancement methods under long-term operation. The insights presented herein provide a valuable theoretical foundation and design-oriented guidance for the rational engineering of high-performance, durable air electrodes for PCCs, thereby contributing to the further development of PCC technology. Finally, future challenges in further development of advanced air electrodes are also discussed. • Hydration/defects are connected to H + /O 2- /e - transport and ORR/OER kinetics in PCC air electrodes. • Humid/CO 2 degradation is consolidated: poisoning, segregation, defect drift, and interfacial failure. • Optimization is hierarchized from bulk and surface to architecture and electrode/electrolyte interfaces. • Commercialization pathways are accelerated by operando tools, DFT-guided descriptors, and AI/ML co-design.