Electrochemical investigation of Y0.5Ca0.5BaCo4−xZnxO7-Ce0.8Sm0.2O2 composite cathode materials for solid oxide fuel cells

This paper investigates Y0.5Ca0.5BaCo4−xZnxO7-Ce0.8Sm0.2O2 (SDC) composite cathode materials for intermediate temperature solid oxide fuel cells (SOFCs). The effects of Zn contents in Y0.5Ca0.5BaCo4−xZnxO7 materials on the electrical conductivity, electrochemical performances and thermal expansion have been systemically studied. It is found that the Y0.5Ca0.5BaCo4−xZnxO7 materials have good electrical conductivity. Sintered Y0.5Ca0.5BaCo3ZnO7 samples show a lowest thermal expansion coefficient (TEC) of about 9.3 × 10−6 K−1. This makes the cathode materials well thermally compatible with SDC electrolytes. XRD results show that the Y0.5Ca0.5BaCo4−xZnxO7 materials are chemically stable to SDC electrolyte. Furthermore, Y0.5Ca0.5BaCo4−xZnxO7-SDC composite cathodes have small area specific resistance (ASR) with SDC electrolyte. The ASR value is 0.05 Ω cm2 at 800 °C and 0.11 Ω cm2 at 750 °C, respectively. Single solid oxide fuel cells based on the Y0.5Ca0.5BaCo3ZnO7-SDC (50:50) composite cathode with SDC as electrolyte and Ni/SDC as anode show maximum power density of 320 mW cm−2, 260 mW cm−2 and 200 mW cm−2 at 700 °C, 650 °C and 600 °C, respectively.