Enhanced electrochemical performance of partially amorphous La0.6Sr0.4CoO3-δ oxygen electrode materials for low-temperature solid oxide cells operating at 400 °C

Abstract

This work evaluates partially amorphous La0.6Sr0.4CoO3-δ (LSC) as a potential oxygen electrode for low-temperature solid oxide cells. LSC was deposited using the spin-coating technique onto Ce0.8Gd0.2O2-δ (CGO) substrates. The optimal oxygen electrode thickness was determined as 500 nm. The electrochemical impedance spectroscopy (EIS) study showed a significant improvement in oxygen reduction/oxidation reaction kinetics when annealing temperatures below 600 °C. The lowest value of the polarisation resistance was observed for the sample annealed at 400 °C, followed by a temperature of 500 °C. EIS measurements at different pO2 content were performed at levels between 0.5 % and 20 %. A comprehensive equivalent circuit analysis was carried out for an explanation of the limiting factors of the catalytic reaction. X-ray absorption fine structure analysis allowed for the identification of differences between crystalline LSC and its partially amorphous form. X-ray absorption near-edge spectroscopy analysis indicated that cobalt adopts a lower oxidation state for the partially amorphous form. Moreover, extended X-ray absorption fine structure analysis indicated the decreased of cobalt oxidation state in partially amorphous LSC. It can be assumed that the increased activity of LSC at temperatures below the crystallization may be due to increased defects and oxygen vacancies in the material.