Investigation on iron-doped lanthanum strontium manganite cathode-LaGaO3 electrolyte interface for oxygen reduction reaction

Pure and 10-30 mol% Fe 2+ doped lanthanum strontium manganite (LSM) was investigated probably for the first time at the interface with lanthanum gallate based electrolyte in symmetric cell mode for oxygen reduction reaction (ORR). The complete phase purity with a rhombohedral structure was confirmed by X-ray diffraction (XRD) after calcining at 1200°C. X-ray photoelectron spectroscopy (XPS) study revealed a much higher Mn 3+ /Mn 4+ ratio and oxygen non-stoichiometry in doped LSM with respect to undoped LSM. The presence of Fe 2+ with an extra satellite peak indicated possibilities of high catalytic activity of multivalancy Mn. Impedance spectroscopy results revealed significantly low area specific resistance (ASR) of LSM electrodes with iron doping. At 800°C, 10 mol% Fe 2+ doped LSM showed the highest conductivity of 75 S/cm and the best cathode performance with lowest ASR value of 0.066 Ω-cm 2 among the studied compositions. The steps of ORR were evaluated from the analysis of the equivalent electrical circuit of impedance data and a suitable model was proposed for this electrochemical reaction. • Iron (Fe 2+ ) doped LSM was first time investigated at the interface with lanthanum gallate electrolyte • The Mn 3+ /Mn 4+ multi-valancy ratio significantly controls ORR catalytic activity and oxygen vacancy • Nominal ionic conductivity generated due to doping is the novelty and it was supported by the experimental results • Very low ASR value with 10 mol% Fe 2+ doped LSM indicates low temperature SOFC application possibility