Electrochemical performance of LaNi0.6Co0.4O3-δ–Ce0.9Gd0.1O1.95 composite electrode and evaluation of its effective reaction length

The electrochemical properties of LaNi0.6Co0.4O3-δ–Ce0.9Gd0.1O1.95 composite electrodes as a function of temperature and p(O2) were investigated by electrochemical impedance spectroscopy. The area-specific conductivity, σE, of the composite electrodes was found higher than the porous LaNi0.6Co0.4O3-δ electrode. The σE greatly depends on their volume ratios, where 70% LaNi0.6Co0.4O3-δ-30% Ce0.9Gd0.1O1.95 showed the highest σE among the compositions. The effective reaction length (lc) of the composite electrodes was estimated by taking the ratio of the calculated capacitance from the impedance analysis to the volume-specific chemical capacitance of LaNi0.6Co0.4O3-δ electrode. The lc is independent of the volume ratio of the composite electrode although the σE greatly depends on their volume ratios, meaning that the lc is independent to the enhancement of σE. Semi-quantitative analysis on the transport properties indicated that the enhancement of the ionic conducting pathway was not the only reason for the enhancement of the electrochemical properties, but also the surface reaction rate of LaNi0.6Co0.4O3-δ was expected to enhance upon contact with Ce0.9Gd0.1O1.95 phase.