Microstructural 3D Reconstruction and Performance Evaluation of LSCF Cathodes Obtained by Electrostatic Spray Deposition

Abstract

Electrostatic spray deposition (ESD) was used to deposit La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) cathode films on dense Ce0.9Gd0.1O2−δ (CGO) electrolytes. LSCF films with different morphologies were obtained by varying the substrate temperature (250 to 450 °C), nozzle-to-substrate distance (15–45 mm) and precursor solution flow rate (0.34 to 1.5 mL h–1). A detailed study on the influence of the microstructure of LSCF cathode films on electrochemical behavior is reported. Resulting films can be classified according to their morphology as dense, cracked and coral microstructures. Detailed microstructural characterization was made by SEM and completed with 3D focused ion beam–scanning electron beam (FIB-SEM) tomography of representative samples. Surface areas of the cathode/pore interfaces, normalized by the cross-sectional area of the support, were found to be 2.0, 24.7, and 28.2 for dense, cracked and coral microstructures, respectively. Electrical measurements were performed at intermediate temperatures (400–600 °C) by AC impedance spectroscopy in air. Area specific polarization resistance, Rpol, values ranged from 6.23 to 0.82 Ω cm2, with lower values corresponding to samples with higher surface areas. Up to three elementary steps were identified in the oxygen reduction reaction of these films. Microstructural parameters determined by FIB-SEM analysis were used to model the electrical performance of the different cathodes, in good agreement with experimental impedance data.