A high-performance Co-free electrode for solid oxide cells: La0.7Sr0.3Cu0.15Fe0.85O3-δ synthesis and characterisation

Abstract

A Co-free perovskite material, La0.7Sr0.3Cu0.15Fe0.85O3-δ, is synthesized and electrochemically characterized to evaluate its potential application as electrocatalyst in the air electrode of solid oxide cells. The powder was firstly synthesized by the sol-gel method and subsequently morphologically and structurally characterized by scanning electron microscope and X-ray diffraction. Symmetrical circular button cells featuring Sm-doped ceria (20% Sm) as supporting electrolyte and La0.7Sr0.3Cu0.15Fe0.85O3-δ as electrocatalyst were manufactured to carry out electrochemical investigations. Two different electrode morphologies are analyzed. In the first structure, the La0.7Sr0.3Cu0.15Fe0.85O3-δ calcined powders are directly deposited by slurry coating on a dense sintered supporting pellet of Sm-doped ceria. In the second electrode configuration, the precursor solution of La0.7Sr0.3Cu0.15Fe0.85O3-δ impregnates a porous scaffold of Sm-doped ceria, previously deposited and co-sintered with the supporting electrolyte. The performance of the samples was studied by means of electrochemical impedance spectroscopy, measuring polarization resistances of 0.0153 Ω∙cm2 at 700 °C and 0.052 Ω∙cm2 at 600 °C for the slurry coated and infiltrated electrodes, respectively. These values, according to the authors knowledge, are amongst the lowest ever obtained for Co-free solid oxides electrodes. However, the very high electrocatalytic activity obtained at intermediate temperatures is not accompanied by chemical stability over time.