Thin film SOFCs with cobalt-infiltrated cathodes

Anode-supported SYSZ [i.e., (Sc 2O 3) 0.1(Y 2O 3) 0.01(ZrO 2) 0.89] thin-film solid oxide fuel cells were evaluated between 650 and 800 °C. Peak power densities and power densities at cell voltages of 0.7 V were 320 and 190 mW/cm 2, respectively, at 650 °C, denoted as 320/190/650. Corresponding power densities at other temperature were 1400/1100/800, 990/640/750, and 600/360/700. At 750 °C and lower, the power densities and ASRs (area-specific resistances) were better than those reported for an 8YSZ cell with record performance [S. de Souza, S.J. Visco, L.C. De Jonghe, in Proceeding of the Second European Solid Oxide Fuel Cell Forum, edited by B. Thorstensen, vol. 2 (1996), 677.], while showing a smaller temperature dependence. Further performance improvements of about a factor of 2 were obtained at 650 °C after infiltration of the LSM/YSZ cathodes with a cobalt solution. This improvement persisted up to about 750 °C, being more pronounced at the lower temperatures. The results indicate the potential benefit of cobalt infiltration for reduced temperature SOFCs. AC measurements revealed that the majority of effect resulted from a decrease in the non-ohmic resistance of the cathode. TEM observations found ∼25 nm Co 3O 4 particles in the pores of the modified LSM-composite cathodes. The AC impedance response following cobalt infiltration indicates a decrease of the effective charge transfer resistance.