Investigation of La_0.65Ca_0.35FeO_3−δ as a Co-Free Cathode for Protonic Ceramic Fuel Cells with Yb-Doped BaZrO₃ Electrolyte

In protonic ceramic fuel cells (PCFCs), the use of cobalt-free cathodes is expected to reduce manufacturing costs and improve durability performance. However, cobalt-free cathodes generally tend to have poor power generation performance due to their lower catalytic activity than cobalt-containing cathodes. Therefore, based on a previous study in which higher power generation performance was obtained with SOFCs using La 0.65 Ca 0.35 FeO 3− δ (LCaF) than with SOFCs using La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3- δ (LSCF) containing cobalt, we focused on LCaF as a cobalt-free cathode. In this study, we attempted to apply cathodes with LCaF to anode-supported PCFCs using a BaZr 0.8 Yb 0.2 O 3- δ (BZYb) electrolyte in order to improve the power generation performance and durability of PCFCs. The proton-conducting oxides used for composite cathodes were investigated. BZYb, which is the same as the electrolyte, was used, but the adhesion between the electrolyte and the cathode was poor. When, BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3- δ (BZCYYb), which has good sinterability compared with BZYb, was therefore used, reading to improvement in the adhesion. Moreover, process parameters such as composite ratio and sintering temperature were also optimized. As a result, a maximum power density of 0.4 W cm -2 at an operating temperature of 600 °C was obtained for PCFCs using a composite cathode of LCaF and BZCYYb at a weight ratio of 6:4 sintered at 1100 °C, which is equivalent to PCFCs using a cathode with LSCF. In addition, the voltage drop rate of PCFCs using a composite cathode of LCaF and BZCYYb in the constant current durability test (0.26 A cm -2 ) at an operating temperature of 600 °C was 4% per 1000 hours, less than 1/10 that of PCFCs using a cathode with LSCF. Based on these results, LCaF is one of the candidate materials of cobalt-free cathode for PCFCs. Acknowledgements: This work is based on the results obtained from a project (JPNP20003) commissioned by the New Energy and Industrial Technology Development Organization (NEDO), Japan.