Counter Electrodes for Electrochemical Evaluation of LSM Electrodes under Polarization

Abstract

LSM electrodes are widely used in both solid oxide fuel cells and solid oxide electrolysis cells. The polarization and impedance behavior of the LSM electrodes are strong functions of the electrode’s prior history, such as current flow and temperature changes. It is desirable to measure polarization and impedance data of the LSM electrodes over a wide range of DC currents. With thin electrolytes, reference electrodes generally fail to isolate the behavior of a single electrode. We describe an alternate strategy in which the LSM electrode is paired with a LSCF counter electrode either on YSZ or on YSZ with a thin SDC layer. The LSCF electrode is quickly created by spray pyrolysis followed by rapid heating to a low sintering temperature. The LSCF electrode exhibits a polarization resistance at least an order of magnitude lower than the polarization resistance of the LSM electrode for cathodic and anodic current densities up to 1 A/cm2. Consequently, the observed polarization and impedance behavior of the cell is unambiguously assignable to the LSM electrode. At 800°C in air, the LSCF electrodes exhibit significant increases in polarization resistance with time, with the rate being lower on YSZ coated with a thin SDC layer. The strategy of creating a low impedance counter electrode by spray pyrolysis is broadly applicable and flexible with respect to electrode composition.