From theory to experiment: BaFe0.125Co0.125Zr0.75O3−δ, a highly promising cathode for intermediate temperature SOFCs
E. Sánchez-Ahijón, R. Marín-Gamero, B. Molero-Sánchez, D. Ávila-Brande, A. Manjón-Sanz, M. T. Fernández-Díaz, E. Morán, R. Schmidt, J. Prado-Gonjal
In a recent theoretical study [Jacobs et al., Adv. Energy Mater., 2018, 8, 1702708], BaFe0.125Co0.125Zr0.75O3−δ was predicted to be a stable phase with outstanding performance as an auspicious cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). It is shown here that the theoretical predictions are valid. The material can be synthesized by the citrate method as a single cubic Pm[3 with combining macron]m phase with a significant amount of oxygen vacancies, randomly distributed in the anionic sublattice facilitating oxygen vacancy conduction. A thermal expansion coefficient of 8.1 × 10−6 K−1 suggests acceptable compatibility with common electrolytes. Electrochemical impedance spectroscopy of symmetrical cells gives an area-specific resistance of 0.33 Ω cm2 at 700 °C and 0.13 Ω cm2 at 800 °C. These values are reduced to 0.13 Ω cm2 at 700 °C and 0.05 Ω cm2 at 800 °C when the material is mixed with 30 wt% Ce0.9Gd0.1O2−δ.
Temperature dependence of BaFe0.125Co0.125Zr0.75O3−δ resistivity ρ. Red circles represent the data determined from the Novocontrol Alpha-A instrument, while green squares correspond to the total electrical resistivity measured by the 4-point method using the Autolab instrument. Solid lines represent the linear fit of the data on Arrhenius axes.