Electrochemical Performance Investigation of Sr(Ti_1-xFe_x)O_{3- δ} Fuel Electrodes with Different Fe Contents for Solid Oxide Electrochemical Cells

Sr(Ti1-xFex)O3-δ (STF) is an alternative to Ni-based cermet fuel electrodes for solid oxide electrochemical cells (SOCs) that can provide an improved tolerance to redox cycling, fuel impurities, and hydrocarbon fuels. Sr(Ti0.3Fe0.7)O3-δ electrodes were recently found to exhibit an excellent performance, but lower Fe contents have not been studied. In this work, the electrochemical performance of STF-based fuel electrodes with 0.4 < x < 0.7 are explored in both full cells and symmetric cells at different fuel conditions. The electrode performance in the fuel cell mode (3% H2O humidified hydrogen) became slightly worse as x decreased from 0.7 to 0.5; however, it was much worse at x = 0.4. In the steam electrolysis mode from 50% H2O to 50% H2, the change in the electrode performance showed a similar trend, and a more significant degradation in the performance was found at x = 0.4. The worse electrochemical performance in a high-steam-concentration atmosphere is due to the higher electrode polarization and increased ohmic resistance. These results indicate that STF electrodes with x = 0.5 have a reasonable electrochemical performance for SOC applications.