Reoxidation behavior of Ni-Fe bimetallic anode substrate in solid oxide fuel cells using a thin LaGaO₃ based film electrolyte

The reoxidation behavior of a Ni-Fe metal anode supported cell using a thin LaGaO₃ electrolyte film was investigated as a function of the reoxidation temperature. After oxidation and reduction treatments for 2 h, the voltage did not return to the initial voltage at higher temperatures (773-973 K); however, after reoxidation at 673 K, the cell exhibited almost the same OCV as the as-prepared cell. During reoxidation with air at the higher temperatures, the Ni-Fe metal substrate exhibited two different expansion behaviors by the different oxidation rates of Ni and Fe. On the other hand, the volumetric change of the oxidized substrate at 673 K was negligible. SEM-EDX results exhibited the reoxidation of Ni-Fe occurred only at the bottom part of the substrate and at the interface between the electrolyte and the substrate. In spite of temperatures as low as 673 K, the cell generated a power of 160 mW cm ^-2, which hardly decreased after the redox cycle. The increasing anodic internal resistance accompanied with unreduced Fe.