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

Abstract

La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) electrode deposited on Gadolinium Doped Ceria (GDC) has been characterized by cyclic voltammetry and impedance spectroscopy in the temperature range of 300–700 °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, Rs, measured on the impedance diagrams as a function of the dc bias. LSCF was deposited with two different microstructures, either porous layer (∼10 μm thick) by screen-printing (SP) or almost dense layer (∼2 μm 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 °C. The Rs 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 Rs was independent on the applied potential from 300 to 700 °C. Decreasing the oxygen partial pressure allowed the peaks to be evidenced and Rs 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.