Study of Ni-YSZ Electrode Capacitance and Its Correlation with the Microstructure

Abstract

Herein, electrochemical measurements are performed on an Ni-dense electrode in a yttria-stabilized zirconia (YSZ) electrolyte to determine the correlation between the measured capacitance ( C m ) and double-phase boundary (DBP) of Ni–YSZ. The Ni-dense electrode is prepared via pulsed-laser deposition by varying the electrode diameter (50–1000 μm), thus revealing that the C m value is proportional to the DPB area. This implies that the capacitance of Ni–YSZ can be used to observe the change in microstructure during operation. This result is confirmed by electrochemical measurements of the Ni–YSZ porous electrode. The impedance spectra of the Ni–YSZ porous electrode from electrochemical measurements are analyzed using a 1D transmission-line model, where the microstructure parameters are determined using scanning electron microscopy. The analysis reveals that the electrode resistance is correlated with the triple-phase boundary length as a function of r p ∝ L Ni − YSZ − 1 , and the electrode capacitance is linearly correlated with the DPB as a function of c p ∝ L Ni − YSZ 2 of Ni–YSZ. Thus, the results from the dense and porous electrodes are used to understand the degradation mode in Ni–YSZ (owing to microstructural changes), which are determined by their capacitance.