The individual electrode processes from anode and cathode have been clearly identified from practical impedance spectra with high-frequency inductive impedances for the Mitsubishi segmented-in-series tubular solid oxide fuel cell by combining the distribution of relaxation time analysis and the complex nonlinear least square fitting. Anodic gas diffusion process and charge transfer reaction near anodic triple phase boundary appear at
∼0.3
and
1000Hz
, respectively. Cathodic oxygen reduction processes appear at
∼10Hz
at
700°C
, whereas the impedance arc over
10000Hz
is dominated by the cathodic oxygen ion transfer through the
(normalLa,normalSr)normalMnO3
(LSM)/
normalY2normalO3
-stabilized
normalZrO2
(YSZ) interface and YSZ of the composite. The results also exhibit an excellent agreement with those from the analysis of difference in impedance spectra.
Gas phase transport is a very important electrode process in practical solid oxide fuel cells. In this study, we have identified gas conversion impedance and gas diffusion impedance in the Mitsubishi segmented-in-series tubular solid oxide fuel cell. Gas conversion impedance is caused by the weak convection transport in the gas flow channel. It is observed that both the insufficient anode and cathode gas flow rates can result in the gas conversion impedance. Gas conversion impedance appears at less than 0.1 Hz, and its magnitude strongly depends on the gas flow rates. It disappears when the gas flow rates of both the anode and cathode are improved sufficiently. Anode gas diffusion through the porous substrate appears at ϳ0.5 Hz and dominates the overall diffusion impedance. Cathode gas diffusion through the porous current collecting layer appears at ϳ3 Hz, which significantly contributes to the overall gas diffusion impedance under low cathode oxygen partial pressures.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.