Oxide composite of La_0.3Sr_0.7Ti_0.3Fe_0.7O_3-Δ and CeO₂ as an active fuel electrode for reversible solid oxide cells

In this paper, La_0.3Sr_0.7Ti_0.3Fe_0.7O_3-δ (LSTF0.7) composite with CeO₂ is successfully prepared by infiltration method as a thin porous electrode and examined in detail as a fuel electrode for efficient reversible solid oxide cells (RSOCs) at different ratios of CO/CO₂ at the temperatures of 700–850 °C. XRD analysis indicates that the cubic perovskite LSTF0.7 is stable in CO or CO₂ at high temperature and compatible with CeO₂ and scandia-stabilized zirconia (ScSZ) electrolyte. In electrolysis mode, the current density of 3.56 A cm⁻² is obtained from the I–V curve at 2.0 V in 50% CO+ 50% CO₂ at the temperature of 850 °C. The polarization resistance (R_p) of the whole cell at 800 °C is 0.28 Ω cm² when 1.4 V is applied in the same gas composition. The corresponding activation energy of the fuel electrode under open circuit is calculated to be 81.37 kJ mol⁻¹. In fuel cell mode, the maximal power density of 437 mW cm⁻² is obtained at 800 °C in 70% CO+ 30% CO₂ as well. The reversible operation at 800 °C indicates that a slow degradation phenomenon in both SOFC and SOEC modes is observed, due to the particle agglomeration of the infiltrated fuel electrode.