An efficient and robust lanthanum strontium cobalt ferrite catalyst as a bifunctional oxygen electrode for reversible solid oxide cells

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 9; no. 9; pp. 557 - 5521
• Main Authors: Kim, Doyeub, Park, Jin Wan, Chae, Munseok S, Jeong, Incheol, Park, Jeong Hwa, Kim, Kyeong Joon, Lee, Jong Jun, Jung, Chanhoon, Lee, Chan-Woo, Hong, Seung-Tae, Lee, Kang Taek
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 09.03.2021
• Subjects: Catalysts; Chemical energy; Chemical reduction; Cobalt; Cobalt ferrites; Density functional theory; Diffusion barriers; Electrical conductivity; Electrical resistivity; Electrodes; Electrolysis; Electrolytic cells; Energy storage; Free energy; Fuel cells; Fuel technology; Heat of formation; Hydrogen-based energy; Lanthanum; Mathematical analysis; Oxygen; Oxygen evolution reactions; Oxygen ions; Oxygen reduction reactions; Perovskite structure; Perovskites; Strontium; Weather; Wind power
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/d0ta11233j

Reversible solid oxide cells (SOCs) are unique devices that perform interconversion between chemical energy (particularly hydrogen) and electricity, providing efficient energy storage for site-specific and weather-dependent solar and wind resources. One of the key requirements for achieving high-performance reversible SOCs is the development of highly active bifunctional catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, we investigate a La 0.2 Sr 0.8 Co 0.8 Fe 0.2 O 3− δ (LSCF2882) material as a novel oxygen electrode for reversible SOCs at intermediate temperatures. Unlike most widely used La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3− δ (LSCF6428) with a rhombohedrally distorted perovskite structure, LSCF2882 possesses a simple cubic perovskite structure with a symmetric BO 6 octahedral network. Furthermore, the 3D bond valence sum calculation of the LSCF2882 structure suggests a reduction in oxygen ion conduction barrier energy. Oxygen surface exchange ( k chem ) and diffusion ( D chem ) coefficients of LSCF2882 determined by electrical conductivity relaxation are consistently remarkably higher by >2 and 20 times compared to those of LSCF6428 at 700 °C, respectively. This result is further supported by a 43% reduction in the oxygen vacancy formation energy of LSCF2882 determined from density functional theory calculations. The reversible SOCs with LSCF2882 oxygen electrodes greatly outperform LSCF6428 cells in both fuel cell (2.55 W cm −2 ) and electrolysis mode (2.09 A cm −2 at 1.3 V) at 800 °C, with excellent reversible cycling stability. Our findings strongly suggest that LSCF2882 is a promising candidate as a bifunctional oxygen electrode for high performance reversible SOCs at reduced temperatures. A perovskite La 0.2 Sr 0.8 Co 0.8 Fe 0.2 O 3− δ catalyst exhibited remarkably high activities for the ORR and OER as a novel bifunctional oxygen electrode for reversible SOCs.