Impedance Studies of the Reduction Process in NiO-YSZ SOFC Anodes

The aim of this study is the development of a methodology for deeper insight into the Ni-YSZ anode behavior by in situ impedance monitoring of the Ni network initial formation and changes during the redox process. The testing is performed on single bare anodes. This approach bypasses complications arising from the impedance data analysis of cells. For more complete description of the changes in the anode microstructure, gas permeability measurements are also introduced. The obtained results show that impedance can register the changes in the sample's conductivity during anode reduction, as well as during redox cycling performed in mild oxidation conditions. The oxidation rate is much slower than the reduction one. The combination of impedance with gas permeability and microstructural measurements gives new opportunities for anode optimization in respect to the ohmic and the concentration polarization