Layered-perovskite oxides with in situ exsolved Co–Fe alloy nanoparticles as highly efficient electrodes for high-temperature carbon dioxide electrolysis

Abstract

Carbon dioxide (CO₂) reduction using solid oxide electrolysis cells (SOECs) has attracted great attention because of the high efficiency and fast kinetics enabled by high operating temperatures. Electrode materials with high catalytic activity for CO₂ reduction and good stability over long-term operation, nevertheless, are still to be developed. In this work, layered-perovskite oxide electrodes with in situ exsolved Co–Fe alloy nanoparticles are developed for efficient CO₂ electrolysis to produce carbon monoxide (CO). Using double perovskite oxide Sr₂Ti_0.8Co_0.2FeO_6−δ as a solid precursor, a Ruddlesden–Popper phase oxide matrix with exsolved Co–Fe alloy nanoparticles uniformly distributed on the surface (Co–Fe–STCF) is synthesized by thermal reduction. The cell with a mixture of Co–Fe–STCF and Sm_0.2Ce_0.8O_2−δ (SDC) as the fuel electrode exhibits outstanding performance for CO₂ electrolysis, with a polarization resistance (R_p) as low as 0.22 Ω cm² at 800 °C. A current density of 1.26 A cm⁻² is acquired at a bias of 1.6 V at 800 °C, and the CO production rate reached 8.75 mL min⁻¹ cm⁻² with a high value of Faraday efficiency (∼100%). Moreover, the Co–Fe–STCF–SDC electrode shows good stability for long-term (100 h) operation with no carbon deposition on the surface. Such high performance of the Co–Fe–STCF–SDC electrode is attributed to abundant oxygen vacancies in the oxide matrix and the high catalytic activity of the exsolved metal nanoparticles. The result of this work can guide the design of highly active and stable (electro)catalysts for high-temperature energy and environmental devices.