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Solid oxide fuel cells (SOFC) have the advantage of being able to operate with fuels other than hydrogen. In particular, liquid fuels are especially attractive for powering portable applications such as small power generators or auxiliary power units, in which case the direct utilization of the fuel would be convenient. Although liquid fuels are easier to handle and transport than hydrogen, their direct use in SOFC can lead to anode deactivation due to carbon formation, especially on traditional nickel/yttria stabilized zirconia (Ni/YSZ) anodes. Significant advances have been made in anodic materials that are resistant to carbon formation but often these materials are less electrochemically active than Ni/YSZ. In this review the challenges of using liquid fuels directly in SOFC, in terms of gas-phase and catalytic reactions within the anode chamber, will be discussed and the alternative anode materials so far investigated will be compared.

The use of a reference electrode (RE) is necessary to independently measure the overpotential of each electrode in solid oxide fuel cells (SOFC). This type of set‐up, known as the 3‐electrode (or 3‐terminal) configuration, can give erroneous results if the RE does not effectively separate the potential of the two active electrodes. In this work, calculations and experiments were performed to verify the effectiveness of the 3‐electrode configuration used in electrochemical impedance spectroscopy (EIS) measurements for studying the kinetics of anodes and cathodes in SOFC. Initially, a theoretical analysis of the impedance distortions in relation to the electrode geometry and configuration is presented and the main causes of distortions are elucidated. Then, this analysis is corroborated by experimental results obtained using two specially designed cells. Calculations and experiments reconfirm that configurations characterised by electrodes of equal area and symmetrical placement do not produce EIS distortions when the electrodes have similar area‐specific polarisation resistances and time constants. Moreover, distortions can be low even in considerably misaligned configurations when electrodes are small and relatively inactive.

The 3‐electrode configuration is commonly applied to quantify the overpotential of anodes or cathodes in solid‐oxide fuel cells (SOFC). In this type of set‐up, a reference electrode (RE) is used to isolate the potential loss of one electrode from that of the entire cell; however, erroneous results can be obtained whenever the RE does not precisely separate the potential drop between the two active electrodes. In this study, we present the results of a theoretical and experimental analysis focused on verifying the effectiveness of the 3‐electrode configuration in electrochemical impedance spectroscopy measurements for the kinetic characterisation of SOFC electrode reactions. The focus of this paper is on the distortion of impedance measurements caused by differences in the area‐specific polarisation resistance and impedance time constants of the working and counter electrodes. The results obtained numerically and experimentally, both for planar and tubular SOFC cell geometries, prove the reliability of the theoretical model used. From the systematic simulation presented here and in our previous work, it was possible to formulate general guidelines for the design of 3‐electrode experimental SOFC. The theoretical model used here can also be used to verify the consistency of EIS measurements obtained with thin planar cells.

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