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.
Published in Journal of The Electrochemical Society, Volume 151, Issue 5, 2004, pages H117-H121.
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Publisher’s Version: http://dx.doi.org/10.1149/1.1688339
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. http://dx.doi.org/10.1149/1.1688339