The electrochemical and thermodynamic characterization of PrBaCo 2− xFe xO 5+ δ ( x = 0, 0.5, 1) infiltrated into yttria-stabilized zirconia scaffold as cathodes for solid oxide fuel cells

Abstract

The effect of Fe substitution for Co on the thermodynamic and electrical properties of the double perovskites, PrBaCo 2− x Fe x O 5+ δ (PBCF, x = 0, 0.5, 1), are investigated as cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). At a given temperature, the electrical conductivity decreases with increasing Fe content, x, in the PBCF–YSZ composites in air. PBCF–YSZ ( x = 1) composite appear to be more stable than PBCF–YSZ ( x = 0) composite down to lower oxygen partial pressure, p(O 2), at the same temperature. The higher oxidation enthalpies of the x = 1 composite can also explain the superior stability at roughly the same p(O 2). The high entropy change for the x = 1 composite can indicate the high probability in the formation of interstitial oxygen at approximately the same p(O 2). Impedance spectra of symmetrical cells (PBCF–YSZ/YSZ/PBCF–YSZ) show lower cathode polarization losses with increasing amounts of Fe. The maximum power densities of x = 0 composite and x = 0.5 composite are 0.68 and 0.72 W cm −2, respectively, at 973 K. The maximum power density of the x = 1 composite is, however, about 20% higher than that of the other composites. Considering redox stability and electrochemical performance, higher Fe content of PrBaCo 2− x Fe x O 5+ δ ( x = 1) is more suitable as a cathode material than x = 0 composite in IT-SOFC application.