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Nd1.8Ce0.2CuO4+δ:Ce0.9Gd0.1O2−δ as a composite cathode for intermediate-temperature solid oxide fuel cells

Authors
Journal
Journal of Power Sources
0378-7753
Publisher
Elsevier
Publication Date
Volume
268
Identifiers
DOI: 10.1016/j.jpowsour.2014.06.130
Keywords
  • Composite Cathode
  • Electrode Polarization Resistance
  • Electrochemical Impedance Spectroscopy
  • Symmetric Cell
  • Particle Size Distribution

Abstract

Abstract The (100 − x)Nd1.8Ce0.2CuO4+δ:(x)Ce0.9Gd0.1O2−δ (x = 00, 10, 20 and 30 vol.%) composite systems are obtained by impregnating a stoichiometric solution of cerium and gadolinium nitrates followed by sintering at 900 °C for 4 h. Impregnating the Ce0.9Gd0.1O2−δ not only inhibits the growth of the host Nd1.8Ce0.2CuO4+δ grains during sintering but also enlarges the oxygen reduction reaction zone by introducing a nanosized phase that is ionically conductive, which significantly decreases the electrode polarization resistance of the composite cathode. A minimum polarization resistance value of 0.23 ± 0.02 Ω cm2 is obtained at 700 °C for a (80)Nd1.8Ce0.2CuO4+δ:(20)Ce0.9Gd0.1O2−δ composite cathode, and this value is attributed to the optimal dispersion into the porous Nd1.8Ce0.2CuO4+δ matrix. The impedance spectra are modeled using an electrical equivalent model that consists of a mid-frequency ZR1–CPE circuit (parallel combination of R1 and constant phase element (CPE)) and a low-frequency Gerischer impedance. The Gerischer impedance decreases significantly when Ce0.9Gd0.1O2−δ infiltrates the Nd1.8Ce0.2CuO4+δ matrix. The oxygen partial pressure-dependent polarization study suggests a medium-frequency response, which is due to charge transfer step; however, the low-frequency response corresponds to the non-charge transfer oxygen adsorption–desorption and the diffusion process during the overall oxygen reduction reaction process.

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