Ruddlesden–Popper oxide SrEu2Fe2O7 as a promising symmetrical electrode for pure CO2 electrolysis

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2021-01, Vol.9 (5), p.2706-2713
• Main Authors: Huan, Daoming, Zhang, Lu, Zhang, Shaowei, Shi, Nai, Li, Xinyu, Zhu, Kang, Xia, Changrong, Peng, Ranran, Lu, Yalin
• Format: Article
• Language: English
• Subjects: Carbon cycle; Carbon dioxide; Cathodes; Circuits; Electrochemistry; Electrode materials; Electrode polarization; Electrodes; Electrolysis; Electrolytic cells; Energy conversion; Energy conversion efficiency; Environmental impact; Fabrication; Oxidation; Polarization; Reducing atmospheres; Structural stability
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/d0ta09585k

Nowadays, effective utilization of CO2 has been a worldwide issue. Among numerous CO2 conversion devices, solid oxide electrolysis cells (SOECs) have drawn special attention due to their high energy conversion efficiency, great potential in carbon cycling, and low environmental impacts. Compared with the typical ones taking asymmetrical configuration, symmetrical SOECs adapting the same oxide materials as both the cathode and anode have the advantages of simplified fabrication procedures, reduced processing costs and minimized compatibility issues. As the appropriate sites for CO2 conversion, cathodes play the key role in determining the performance of symmetrical SOECs, and thus, attract more attention to improve their electrocatalytic behaviors and endurance via exploring novel materials. In this work, Eu-doped Ruddlesden–Popper (R–P) oxide, SrEu2Fe2O7 (SEF), is applied as an electrode material for symmetrical SOECs to directly electrolyze pure CO2. The outstanding structural stability and excellent electrochemical activity of the SEF electrode under both oxidizing and reducing atmospheres are demonstrated, and relatively low polarization resistances of 0.07 Ω cm2 in air and 0.48 Ω cm2 in 2CO2–CO mixtures at 800 °C are observed. A great current density of 1.27 A cm−2 at an applied voltage of 1.5 V and 800 °C is achieved on this symmetrical SOEC. An extremely low polarization resistance of 0.27 Ω cm2 is also observed under open circuit conditions. Further, the symmetrical button cell has demonstrated excellent stability within 260 h of the long-term CO2 electrolysis test.