Fe-substituted SrTiO_3-δ-Ce_0.9Gd _0.1O₂ composite anodes for solid oxide fuel cells

A new composite solid oxide fuel cell anode material, SrTi _1-xFe_xO_3-δ mixed with Gd-doped ceria, was tested in La_0.9Sr_0.1Ga_0.8Mg _0.2O_3-δ electrolyte-supported cells with La _0.4Ce_0.6O₂ barrier layers and La _0.6Sr_0.4Fe_0.8Co_0.2O₃ cathodes. The x = 0.7 composition had an anode polarization resistance of 0.17 Ω cm², at 800 °C in humidified H₂, much lower than the value 0.39 Ω cm² measured for x = 0.4 and 3.14 Ω cm² for x = 0. The reduced polarization resistance correlated with increased oxygen non-stoichiometry δ, which suggests that it may be related to increased ionic conductivity. Electrochemical impedance spectroscopy (EIS) measurements at 800 °C on the x = 0.7 anode cell showed a main response centered at ∼1 Hz that increased with decreasing hydrogen partial pressure. The maximum power density observed was for the x = 0.7 cell-337 mW cm^-2 at 800 °C in air and humidified hydrogen-and was limited mainly by the thick electrolyte.