Novel cobalt‐free family of SrFe1‐xScxO3‐δ perovskite materials for cathode applications in solid oxide fuel cells

• Published in: International journal of energy research Vol. 44; no. 14; pp. 11702 - 11710
• Main Authors: Li, Yan, Larralde, Ana Laura, Cai, Jiawei, Du, Shunli, Troncoso, Loreto, Fernández‐Díaz, María Teresa, Alonso, José Antonio
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Inc 01-11-2020; Hindawi Limited
• Subjects: cathode; Cathodes; Cobalt; Crystal structure; Crystallography; Electrode materials; Electrolytes; Electrolytic cells; energy conversion; Fuel cells; Fuel technology; Heavy metals; Maximum power density; Neutron diffraction; Oxides; Oxygen; oxygen vacancies; Perovskites; Porous materials; Scandium; SOFC; Solid oxide fuel cells; strontium iron scandium perovskite; Unit cell; Vacancies
• ISSN: 0363-907X; 1099-114X
• DOI: 10.1002/er.5797

Summary
Perovskites of composition SrFe1‐xScxO3‐δ (x = 0.05, 0.1, 0.2) were elaborated, characterized, and tested in solid‐oxide fuel cells (SOFC) as cathode materials. Porous materials were obtained by a solid‐state route. Thermogravimetric studies showed that the oxides eliminate oxygen as temperature increases. Neutron powder diffraction (NPD) experiments unveils that, at 800°C, the crystallographic structure of SrFe0.9Sc0.1O3‐δ contains δ = 0.51 (2) vacancies at oxygen sites, located at random in the cubic unit cell. The oxygen vacancies are essential for the oxygen diffusion, which is prerequisite for a MIEC‐type cathode. The electronic conductivity σ exhibits an insulator‐to‐metal transition at 420°C, reaching almost 200 S cm−1 for x = 0.05; σ was found to decrease as the Sc content increases. The cell performance was tested on electrolyte supported single cells, with LSGM electrolyte, fed by pure H2. The maximum power density reached by the Sc‐ferrite (x = 0.05) was of 340 mW cm−2 at 800°C.
The replacement of Fe for Sc in the SrFe1‐xScxO3‐δ perovskite system stabilizes and expands the cubic crystal structure, driving MIEC properties that are important for its performance as cathode materials in SOFC devices. The performance has been tested in single cells, as shown.