Electrochemical characterization of multi-element-doped ceria as potential anodes for SOFCs

Electrical conductivity of multi- element (Ca, Mn, Y)-doped ceria have been investigated using ac impedance measurement in the temperature range of 300-800 °C under air and H₂. Fluorite-type metal oxides of the nominal chemical compositions Ce_0.89Y_0.1Mn_0.01O _2-δ (CYMO), and Ce_0.87Y_0.1Mn _0.01M_0.02O_2-δ (M = Ca, Mg) were prepared via conventional ceramic (solid state) and combustion methods. The maximum total electrical conductivity of 0.2 S cm^{- 1} at 700 °C in H ₂ was observed for both Mg and or Ca-doped CYMO prepared via ceramic method at 1400 °C. The chemical compatibility of Mg-doped CYMO with 8 mol% yttria-stabilized zirconia (8YSZ) was investigated by powder X-ray diffraction (PXRD), which has shown reactivity between the mixed powders at above 1100 °C in air. Furthermore, scanning electron microscope (SEM) of cross-section area of CYMO/YSZ/CYMO cell configuration discerned formation of a diffusion dense zone at the interface with aggregates of different sizes embedded in the anode layer. The electrochemical performance of the anode has been studied in a symmetrical cell configuration in humidified H₂ at 600-800 °C under open circuit condition. Area specific polarization (ASR) resistance of Mg-CYMO was found to be 0.225 Ω cm² at 800 °C and is comparable to Ni-Cu-CeO₂ and La_0.65Ce_0.1Sr _0.25Cr_0.5Mn_0.5O_3-δ (0.2 Ω cm²) under the comparable measurement conditions.