Study of Activation Effect of Anodic Current on La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ Air Electrode in Solid Oxide Electrolyzer Cell

Electrochemical performance evolution of La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF) air electrode polarized with anodic current is reported in this paper. The study was conducted on three-electrode half-cells with Yttria stabilized zirconia (YSZ) electrolyte using electrochemical impedance spectroscopy under equilibrium potential. Initially, the polarization resistance (R_P) tested at 800 °C of the LSCF electrode sintered at 900 °C is 0.25 Ω cm². During the first 20 hours of testing with anodic current density of 0.2 A cm^-2, R_P increased with a linear dependence on the square root of time, suggesting Sr surface segregation. After the first phase of tests R_P stabilized at 0.68 Ω cm². Continued testing at increased current density to 0.5 A cm^-2 showed that R_P decreased from 0.68 to 0.46 Ω cm², and again to 0.39 Ω cm² at even higher bias of 1 A cm^-2. Moreover, short-term tests for 129 h under various currents again showed that R_P decreased upon higher anodic current while increased upon lower anodic current. However, no obvious degradation on R_P was shown by comparing the value before and after the test. Based on above results, the authors speculate that the application of anodic current may be able to stabilize and activate the performance of LSCF electrode through suppressing and mitigating Sr surface segregation.