Cyclic voltammetry and high-frequency series resistance of La0.6Sr0.4Co0.2Fe0.8O3-δ electrode deposited on GDC: Effect of the electrode microstructure and the oxygen partial pressure

La0.6Sr0.4Co0.2Fe0.8O3-delta (LSCF) electrode deposited on Gadolinium Doped Ceria (GDC) has been characterized by cyclic voltammetry and impedance spectroscopy in the temperature range of 300-700 degrees C. We demonstrate that the LSCF microstructure has a strong influence on the shape of the voltammograms and on the variation of the series resistance, R-s, measured on the impedance diagrams as a function of the dc bias. LSCF was deposited with two different microstructures, either porous layer (similar to 10 mu m thick) by screen-printing (SP) or almost dense layer (similar to 2 mu m thick) by Electrostatic Spray Deposition (ESD). For the denser film, one cathodic peak and one reverse anodic peak were evidenced under air at 300 and 500 degrees C. The R-s value was also found to increase with the dc cathodic bias. On the contrary, no peak was observed with the porous film under the same conditions and R-s was independent on the applied potential from 300 to 700 degrees C. Decreasing the oxygen partial pressure allowed the peaks to be evidenced and R-s to vary. The results are discussed in terms of oxygen exchange rate at the LSCF/gas interface, which depends on the LSCF specific surface area and the oxygen partial pressure. (C) 2019 Published by Elsevier Ltd.