Perovskite air electrodes for reversible protonic ceramic electrochemical cells: Architecture design and degradation mitigation

Reversible Protonic Ceramic Electrochemical Cells (R-PCECs) have emerged as a cutting-edge technology for efficient energy storage and conversion, boasting distinct advantages in fuel flexibility, high energy efficiency, and low operating temperatures compared to traditional solid oxide devices. This review centers on the critical role of air electrodes in R-PCECs, delving into the design principles of multifunctional air electrode architectures and strategies for mitigating degradation mechanisms. It commences by outlining the fundamental working principles of R-PCECs in both fuel cell and electrolysis modes, with a particular emphasis on the pivotal functions of air electrodes in facilitating oxygen reduction and evolution reactions. Subsequently, it systematically elaborates on various advanced air electrode designs, encompassing composite electrode structures, perovskite optimization strategies, and defect-mediated performance enhancement techniques. Additionally, the paper analyzes key degradation pathways such as pollutant-induced failure and structural deterioration, and presents corresponding mitigation approaches involving material engineering, operational parameter optimization, and surface modification. Finally, the current challenges and future research directions in the development of high-performance, durable air electrodes for R-PCECs are highlighted, aiming to guide the advancement of this transformative energy technology.