Evaluation of LSF based SOFC cathodes using cone-shaped electrodes and EIS

• Published in: Solid state ionics Vol. 344; p. 115096
• Main Author: Hansen, K. Kammer
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.01.2020; Elsevier BV
• Subjects: Chemicals; Composition; Dilatometry; Electrochemical impedance spectroscopy; Electrodes; Glycine; Nitrates; Oxygen reduction reactions; Perovskite; Perovskite structure; Perovskites; Solid oxide fuel cells; Spectrum analysis; Strontium compounds; Thermal expansion; Vacancies; X ray powder diffraction
• ISSN: 0167-2738; 1872-7689
• DOI: 10.1016/j.ssi.2019.115096

Seven compositions of (La1-xSrx)0.99FeO3-δ (x = 0, 0.05, 0.15, 0.25, 0.35, 0.50, 0.70) perovskites were synthesized using the glycine-nitrate method. The (La1-xSrx)0.99FeO3-δ compounds were characterized with powder X-ray diffraction, dilatometry, total conductivity and electrochemical impedance spectroscopy on cone-shaped electrodes using a Ce1.9Gd0.1O1.95 electrolyte. Dilatometry shows that the thermal expansion coefficient of the (La1-xSrx)0.99FeO3-δ compounds increases with increasing strontium content. Total conductivity finds is maximum for LSF35. The activity of the (La1-xSrx)0.99FeO3-δ based perovskites towards the electrochemical reduction of oxygen was strongly dependent of the strontium content, the activity being highest for the composition (La0.85Sr0.15)0.99FeO3-δ. The results indicates that Fe(III) is the catalytic active specie towards the electrochemical reduction of oxygen in a solid oxide fuel cell on (La1-xSrx)0.99FeO3-δ compounds. The results also show that oxide ion vacancies in the perovskite structure are important for the electrochemical reduction of oxygen. However, a negative effect of defect ordering (Sr2+ and oxide ion vacancies) is strongly indicated for the strontium rich compounds. Segregation of SrO to the surface might also play a detrimental effect on the activity towards the oxygen reduction reaction. •The effect of replacing lanthanum with strontium is investigated.•It is shown that the lowest polarization resistance is found for the intermediate compound LSF15.•This is thought to be due to a balance between amount of oxygen vacancies, and the amount of Fe(III).