Tuning layer-structured La0.6Sr1.4MnO4+δ into a promising electrode for intermediate-temperature symmetrical solid oxide fuel cells through surface modification

Abstract

A K₂NiF₄-type layer-structured oxide, La_0.6Sr_1.4MnO_4+δ (LSMO₄), is tuned into a potential electrode for intermediate-temperature symmetrical solid oxide fuel cells (IT-SSOFCs) through surface modification. Bulk-phase LSMO₄ shows high chemical stability under both oxidizing and reducing atmospheres and good thermo-mechanical compatibility with the Sm_0.2Ce_0.8O_1.9 (SDC) electrolyte; however, it exhibits insufficient electro-catalytic activity for both the oxygen reduction reaction (ORR) and oxidation of fuels. Surface modification through infiltration is applied to improve the electro-catalytic activity of the LSMO₄-based electrode; both SDC and NiO are explored. The co-modification of the LSMO₄ electrode with SDC and NiO is found to provide the best performance. In particular, LSMO₄–SDC–NiO shows the highest cathodic performance with an area specific resistance (ASR) of only 0.17 Ω cm² at 700 °C. Under optimized conditions, a maximum power density of 614 mW cm⁻² at 800 °C is achieved for an electrolyte-supported symmetrical SOFC with surface modified LSMO₄-based electrodes operating with hydrogen, and a 378 mW cm⁻² maximum power output is still achieved at 800 °C when methane is applied as the fuel. The symmetrical cell also shows good operational stability with both hydrogen and methane fuels. Through proper surface modification based on the infiltration method, the results demonstrate that LSMO₄ can be developed into favorable electrodes for IT-SSOFCs, which are capable of operating with both hydrogen and hydrocarbon fuels.