Reaction Process in the Ni-SDC Cermet Anode

抄録

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 (σ^SDC) for each rate controlling steps were obtained from the impedance spectra. Hydrogen and water vapor pressure (P_H2 and P_H2O, 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 σ^SDC obtained at the lowest frequency region (σ_L^SDC) shows slightly negative dependence on the T and it was proportional to the P_H2O. The σ_M^SDC obtained in the middle frequency region is activated with increasing P_H2, P_H2O and T. This process should be associated with the electrochemical oxidation reaction step accompanied with charge transfer. The σ_H^SDC obtained at the highest frequency region is independent on both P_H2 and P_H2O, 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.