Abstract
Electrochemical frequency modulation (EFM), a non-linear electrochemical technique was applied for the first time to solid oxide fuel cells (SOFC) to obtain effective exchange current density and transfer coefficient values. EFM has been used extensively in corrosion studies and this study investigates the feasibility of the technique in determining kinetic parameters in a SOFC. The study was carried out on a sub-commercial SOFC stack at 750 °C running on 3 % humidified H2. Values obtained from EFM data were compared to values obtained from electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV) at similar operating conditions. A kinetic model based on generalized Butler-Volmer equation was used as the basis for the analysis. The results indicated that the values obtained via EFM were in agreement with EIS and Tafel analyses. The obtained values for a cell within a SOFC stack closely ranged from 11 - 16 mA cm-2 for effective exchange current density and 0.88 – 1.3 for transfer coefficient with good consistency. The values obtained from EFM were also further validated using theoretically developed equations for the specific operating condition. Causality factors, an internal check in EFM which relates the input potential to the output current, was also used to verify the validity of the data obtained by EFM.
Published Version
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