Ru exsolution in substituted La0.75Sr0.25Cr0.5Mn0.5O3-δ compound as anode material for an IT-SOFCs

Highlights: • Synthesis of a Ru substituted La_0.75Sr_0.25Cr_0.5Mn_0.5O_3-δ compound is presented and its total conductivity is measured. • The total conductivity of LSC_0.4MRu_0.1 is mainly electronic and is much higher than that of LSCM_0.3Ni_0.2 and LSCM. • LSC_0.4MRu_0.1 presents a dispersion of Ru particles on the surface of its grain after reduction at 1000 °C. • LSC_0.4MRu_0.1 symmetrical cell exhibits the lowest Rp, 0.087 Ω cm² under Ar/H₂ 5% and 0.04 Ω cm² under methane at 600 °C. In this study, the synthesis of La_0.75Sr_0.25Cr_0.4Mn_0.5Ru_0.1O_3-δ a (LSC_0.4MRu_0.1) compound is presented and its total conductivity is measured and compared with that of La_0.75Sr_0.25Cr_0.5Mn_0.5O_3-δ (LSCM) and the Ni-substituted compound La_0.75Sr_0.25Cr_0.5Mn_0.3Ni_0.2O_3-δ (LSCM_0.3Ni_0.2). While the substitution of Ni decreased LSCM conductivity under a reducing atmosphere, an increase of the total conductivity of Ru substituted phase is evidenced. The reduction of Ni and Ru-substituted LSCM under Ar/H₂ 5% up to 800 °C or 1000 °C respectively leads to the exsolution of nanoparticles, but also to a slight decomposition for the Ru-substituted compound. However, the use of these reduced materials as anode for solid oxide fuel cell (SOFC) in symmetrical cells based on Ce_0.9Gd_0.1O_1.95 (CGO) electrolyte implies not reducing the total system at a temperature higher than 600 °C to avoid ceria reduction. The solution consists of pre-reducing the electrode materials at their exsolution temperature before casting them on CGO thin disk. Under reductive atmospheres, Electrochemical impedance spectroscopy study of symmetrical cells suggests that the exsolution approach improves the adsorption of gaseous species compared to LSCM. LSC_0.4MRu_0.1 symmetrical cell exhibits the lowest polarization resistance, 0.087 Ω cm² under Ar/H₂ (5%) and 0.044 Ω cm² under methane at 600 °C.