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The effects of cathodic dc bias, bulk pO2, and effective O2 -diffusivity on ac impedance spectra of Siemens Westinghouse Power Corporation’s cathode-supported solid oxide fuel cells were systematically studied over a temperature range of 800 to 1000°C. It was found that the activation process dominated the overall electrode kinetics at 800°C, by which the applied dc bias reduced the electrode resistance considerably. With increasing the temperature to above 900°C, the activation process became effectively activated, leading to a visible arc at the lowest frequency on the impedance spectrum, which is relevant to the pore gas-diffusion process. Under this circumstance, lower bulk pO2 and lower effective O2 diffusivity were shown in ac impedance spectra to increase pore gas-diffusion polarization as predicted by the gas-diffusion theory shown in part I of this paper. DC bias was also found to greatly affect the gas-diffusion process as a result of increased dc current.


©Journal of The Electrochemical Society 2004, The Electrochemical Society.

© The Electrochemical Society, Inc. 2004. All rights reserved. Except as provided under U.S. copyright law, this work may not be reproduced, resold, distributed, or modified without the express permission of The Electrochemical Society (ECS). The archival version of this work was published in Journal of The Electrochemical Society].

Publisher’s Version:

Huang, K. (2004). Gas-Diffusion Process in a Tubular Cathode Substrate of a SOFC, Part II: Identification of Gas-Diffusion Process Using AC Impedance Method. Journal of The Electrochemical Society, 151 (5), H117 - H121.