Reaction Process in the Ni-SDC Cermet Anode

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The reaction process for the Ni-SDC cermet anode on the ScSZ electrolyte was examined by impedance spectrometry with wet hydrogen fuels and results were compared with previously obtained data for the Ni-ScSZ anode. Area specific conductivities (σSDC) for each rate controlling steps were obtained from the impedance spectra. Hydrogen and water vapor pressure (PH2 and PH2O, respectively) dependencies and temperature (T) dependence of σ for the Ni-SDC are compared with those of the Ni-ScSZ. Three rate controlling steps were observed for the Ni-SDC anode. The σSDC obtained at the lowest frequency region (σLSDC) shows slightly negative dependence on the T and it was proportional to the PH2O. The σMSDC obtained in the middle frequency region is activated with increasing PH2, PH2O and T. This process should be associated with the electrochemical oxidation reaction step accompanied with charge transfer. The σHSDC obtained at the highest frequency region is independent on both PH2 and PH2O, but it is activated with increasing temperature. This process appears only in the Ni-SDC anode, and therefore, it is reasonable to assume formation of proton at the Ni/SDC interface. The difference in reaction processes between the Ni-SDC anode and the Ni-ScSZ anode is discussed.
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