Recent research trends in layered perovskite-type air electrodes for reversible protonic ceramic cells

systems at intermediate temperatures (400-600oC) due to their remarkable capability for reversible operation in both hydrogen production and electricity generation. To successfully implement this system, intensive research is mainly focused on the development of air electrodes with outstanding chemical stability, catalytic properties, and structural flexibility. This review provides a detailed overview and summary of the recent research trends on layered perovskite-type air electrodes for R-PCCs. In particular, the effects of A-, A’-, and B-site doping elements into a chemical formula of AA’B2O5+δ of layered perovskite structure, where A is a trivalent lanthanide, A’ is an alkaline earth element, and B is a transition metal ion are discussed. Furthermore, the final section presents suggestions for future studies and emphasizes the possibility of improving the electrochemical performance for highly efficient R-PCCs.