Recent advances in atomic-scale simulations for the design of air electrode materials in protonic ceramic fuel cells (PCFCs)

This review article introduces the recent advances in atomic-scale simulations for the design of perovskite-type air electrode materials in protonic ceramic fuel cells (PCFCs). Since the key mechanisms of surface and bulk reactions in PCFCs occur at the atomic scale, atomic-scale simulations have been widely applied for the design of electrode materials in PCFCs. In particular, density functional theory (DFT) is the most common method for investigating these phenomena. Based on both theoretical and experimental results, we found that DFT-calculated hydration and oxygen vacancy formation energies are the key factors in examining the activity of air electrode materials in PCFCs. In addition, those factors can be tuned by not only the change of B-O bond lengths but also the composition of electrode materials. This paper also briefly covers the recently highlighted composite and mixed types of air electrode materials.