A range of solid electrolyte cell geometries has been evaluated in terms of their suitability for measurements of the working electrode polarization resistance in a three-electrode configuration. The potential and current density distributions in the cells are calculated numerically. If the current density at the working electrode is not uniform, the standard procedure of evaluating the electrode polarization resistance from the experimental data is inadequate and may lead to erroneous results. Simulations are presented for cells with thin electrolytes and for pellet-based geometries with large electrolyte thickness. Working electrode C Solid electrolyte Counter electrode 1184

Many processes contribute to the overall impedance of an electrochemical cell, and these may be difficult to separate in the impedance spectrum. Here, we present an investigation of a solid oxide fuel cell based on differences in impedance spectra due to a change of operating parameters and present the result as the derivative of the impedance with respect to ln(f) . The method is used to separate the anode and cathode contributions and to identify various types of processes.

No abstract

No abstract

Cathodes prepared by infiltration of La 0.6 Sr 0.4 CoO 3Àd (LSC40) into a porous Ce 0.9 Gd 0.1 O 1.95 (CGO10) backbone have been developed for low temperature solid oxide fuel cells. The CGO10 backbone has been prepared by screen printing a CGO10 ink on both sides of a 180 m dense CGO10 electrolyte-tape followed by firing. LSC40 was introduced into the CGO10 porous backbone by multiple infiltrations of aqueous nitrate solutions followed by firing at 350 C. A systematic study of the performance of the cathodes was performed by varying the CGO10 backbone firing temperature, the LSC40 firing temperature and the number of infiltrations. The cathode polarization resistance was measured using electrochemical impedance spectroscopy on symmetrical cells in ambient air, while the resulting structures were characterized by scanning electron microscopy (SEM) and high temperature X-ray diffraction (HT-XRD). The firing temperature of 600 C for the LSC40 infiltrate was found to provide a balance between LSC40 material formation and high surface area micro=nanostructure. The lowest polarization resistances measured at 600 and 400 C were 0.044 and 2.3 X cm 2 in air, respectively. During degradation tests at 600 C, the cathode polarization resistance levels out after about 450 h of testing, giving a final polarization resistance of 0.07 X cm 2 .

No abstract

No abstract

No abstract