Ruddlesden–Popper perovskite oxides as emerging air electrodes for protonic ceramic cells

Abstract

Protonic ceramic cells (PCCs) based on proton-conducting electrolytes have been considered as a promising technology for green hydrogen/electricity generation due to their reduced operating temperatures, enhanced conversion efficiencies, improved safety/stability and simplified water management as compared with traditional high-temperature oxygen-ion-conducting solid oxide cells (O-SOCs). Nevertheless, the performance of PCCs is remarkably restricted by the sluggish kinetics of oxygen reduction/evolution reactions (ORR/OER) on air electrodes, especially under low-temperature and high-water-vapor conditions. Although remarkable advancements have been achieved recently, developing optimal air electrodes for high-performance PCCs still remains challenging. Herein, an in-time review about the recent advancements in designing Ruddlesden–Popper perovskite oxides as emerging air electrodes for PCCs is presented by emphasizing the operating principles, requirements for high-performance air electrodes and the superiority/unique features of Ruddlesden–Popper perovskite oxides compared to their single perovskite and double perovskite-based counterparts. Several unique design strategies to enhance the ORR/OER activity/durability and thermo-mechanical compatibility of Ruddlesden–Popper perovskite-based air electrodes for PCCs are also proposed. Finally, current limitations, remaining challenges and future directions are presented. This review tends to present essential guidelines for rationally designing highly efficient and long-lasting air electrodes for next-generation PCCs to facilitate industrial applications.