Durability Improvement of Protonic Ceramic Fuel Cells by High Temperature Sintered Cobalt-Free (La,Ca)FeO<sub>3−</sub><i><sub>δ</sub></i> Based Cathodes

The durability of protonic ceramic fuel cells (PCFCs) decreases owing to Co diffusion from the cathode into the electrolyte. To prevent Co diffusion during high-temperature cathode sintering and improve PCFC durability, this study proposes two methods: (1) low-temperature sintering of the Co-containing cathode and (2) the use of a Co-free cathode. Durability studies were conducted using anode-supported PCFCs with different cathodes: La0.6Sr0.4CoO3−δ (LSCo)–BaCe0.7Zr0.1Y0.1Yb0.1O3−δ (BCZYYb) sintered at 900 and 1100 °C, and La0.65Ca0.35FeO3−δ (LCaF)–BCZYYb sintered at 1100 °C. Both cells with LSCo–BCZYYb cathodes exhibited low durability, regardless of sintering temperature. In contrast, cells with LCaF–BCZYYb cathodes demonstrated higher durability due to the absence of elemental diffusion and good adhesion at the cathode–electrolyte interface. The LCaF–BCZYYb cathode is a promising candidate for high-durability applications in PCFCs.