Functional properties and electrochemical performance of Ca-doped Sr2-x Ca x Fe1.5Mo0.5O6-δ as anode for solid oxide fuel cells

Performance of Ca-doped strontium ferrite-molybdate Sr2-xCaxFe1.5Mo0.5O6-δ (x = 0, 0.05, 0.15, 0.3, 0.5) has been studied under reducing conditions. Thermogravimetry (TG) analysis in 5% H2/Ar and DSC measurements in high-purity argon demonstrated that the compositions are highly stable and there are no phase transitions. The best electrochemical and electrical performances of about 0.12 Ω cm2 and 33 S/cm at 800 °C in wet hydrogen, respectively, were obtained for the Sr1.85Ca0.15Fe1.5Mo0.5O6-δ anode. The EIS spectra were analyzed by means of distribution relaxation times and non-linear least squares methods, which made it possible to determine the behavior of the rate-limiting steps of hydrogen oxidation. Solid oxide fuel cells (SOFC) of planar design with the 1.5 mm LaGaO3-based supporting electrolyte, with the Sr1.85Ca0.15Fe1.5Mo0.5O6-δ symmetrical electrodes and with the Sr2-xCaxFe1.5Mo0.5O6-δ (x = 0.15 and 0.3) anode and the 70 wt% Pr0.9Y0.1BaCo2O6–δ + 30 wt% SDC cathode have been studied. The obtained results demonstrated a low anode overvoltage, which was about 0.12 V at 1 A/cm2 and 800 °C in wet hydrogen. The maximum power density of SOFC with the Sr1.85Ca0.15Fe1.5Mo0.5O6-δ anode and cobaltite cathode was about 0.18 W/cm2 at 800 °С under air/wet hydrogen conditions. The obtained results elucidate that Sr1.85Ca0.15Fe1.5Mo0.5O6-δ is a promising anode for solid oxide fuel cells.