CO₂-to-CO conversion on layered perovskite with in situ exsolved Co–Fe alloy nanoparticles: an active and stable cathode for solid oxide electrolysis cells

To reduce the greenhouse effects due to the massive emission of CO₂, efficient reduction of carbon footprint and effective utilization of CO₂ have been a crucial research field worldwide in the past few decades. Novel catalysts efficiently facilitating the conversion of CO₂ into target chemicals are highly desirable. Herein, we developed a new cathode with in situ exsolved Co–Fe alloy nanoparticles embedded in an active (Pr₀.₄Sr₀.₆)₃(Fe₀.₈₅Mo₀.₁₅)₂O₇ (PSFM) double-layered perovskite backbone (Co–Fe–PSFM), which acts as a more stable and efficient catalyst to promote CO₂ electrolysis in a high temperature solid oxide electrolysis cell (SOEC) compared to the Pr₀.₄Sr₀.₆Co₀.₂Fe₀.₇Mo₀.₁O₃₋δ (PSCFM) cubic perovskite. This newly developed material shows superb redox reversibility between reduction and re-oxidation cycles. Additionally, a remarkable current density of 1.01 A cm⁻² of the SOEC with the Co–Fe–PSFM cathode in conjunction with an impressive polarization area-specific resistance (ASR) as low as 0.455 Ω cm² of the cathode was achieved at 1.6 V and 850 °C. In particular, a high value of Faraday efficiency (∼93%) was achieved at 0.8 V (vs. OCV) and 850 °C. More importantly, the cell with the new cathode shows no observable degradation and carbon formation at 850 °C over a period of 100 h at a constant applied potential. The improved oxygen vacancies resulted from the exsolving process, and phase change (cubic perovskite to double-layered perovskite), together with the exsolved Co–Fe alloy nanoparticles, contributed to the improved catalytic activity, high Faraday efficiency, good stability, and excellent coking resistance for CO₂ electrolysis. In light of the properties above, double-layered PSFM socketed with Co–Fe alloy nanoparticles is an attractive ceramic material for intermediate/high temperature applications, especially for CO₂ electrolysis.