Fabrication of Low Ni-Containing SOFC Anode Using Mixed Ionic and Electronic Conductors

Typical anodes of solid oxide fuel cell consist of a cermet of electronic conductor such as Ni and oxygen ion conductor such as yttria-stabilized zirconia, and have porous structure to enlarge reaction sites. It has been recognized that volume expansion of the Ni species during redox cycle can damage the anode structure and that sintering of the Ni species results in degradation of power generation characteristics. One possible approach for lessening these undesirable effects is to reduce the amount of Ni in the anode, whereas reduced Ni amount in turn decreases the anodic reaction sites. In this study, Ni-SDC (samaria-doped ceria) cermet was prepared by changing SDC particle size and Ni content, and I-V and AC impedance measurement were conducted to evaluate the electrochemical processes that influence the performance of the anode by introducing ΔZ'spectra. It was found that large SDC particles were effective in reducing ohmic overpotential even with low Ni content, and that the conductivity change in the anode with Ni content can be explained by percolation theory.