In this paper, La0.3Sr0.7Ti0.3Fe0.7O3-delta (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 700850 degrees 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 IV curve at 2.0 V in 50% CO+ 50% CO2 at the temperature of 850 degrees C. The polarization resistance (R-p) of the whole cell at 800 degrees C is 0.28 Omega cm(2) 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 degrees C in 70% CO+ 30% CO2 as well. The reversible operation at 800 degrees 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.