Unlocking the Potential of A-Site Ca-Doped LaCo_0.2Fe_0.8O_3-δ: A Redox-Stable Cathode Material Enabling High Current...

Massive carbon dioxide (CO₂) emission from recent human industrialization has affected the global ecosystem and raised great concern for environmental sustainability. The solid oxide electrolysis cell (SOEC) is a promising energy conversion device capable of efficiently converting CO₂ into valuable chemicals using renewable energy sources. However, Sr-containing cathode materials face the challenge of Sr carbonation during CO₂ electrolysis, which greatly affects the energy conversion efficiency and long-term stability. Thus, A-site Ca-doped La_1-CaCo_0.2Fe_0.8O_3-δ (0.2 ≤ x ≤ 0.6) oxides are developed for direct CO₂ conversion to carbon monoxide (CO) in an intermediate-temperature SOEC (IT-SOEC). With a polarization resistance as low as 0.18 Ω cm² in pure CO₂ atmosphere, a remarkable current density of 2.24 A cm^-2 was achieved at 1.5 V with La_0.6Ca_0.4Co_0.2Fe_0.8O_3-δ (LCCF64) as the cathode in La_0.8Sr_0.2Ga_0.83Mg_0.17O_3-δ (LSGM) electrolyte (300 μm) supported electrolysis cells using La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF) as the air electrode at 800 °C. Furthermore, symmetrical cells with LCCF64 as the electrodes also show promising electrolysis performance of 1.78 A cm^-2 at 1.5 V at 800 °C. In addition, stable cell performance has been achieved on direct CO₂ electrolysis at an applied constant current of 0.5 A cm^-2 at 800 °C. The easily removable carbonate intermediate produced during direct CO₂ electrolysis makes LCCF64 a promising regenerable cathode. The outstanding electrocatalytic performance of the LCCF64 cathode is ascribed to the highly active and stable metal/perovskite interfaces that resulted from the in situ exsolved Co/CoFe nanoparticles and the additional oxygen vacancies originated from the Ca₂Fe₂O₅ phase synergistically providing active sites for CO₂ adsorption and electrolysis. This study offers a novel approach to design catalysts with high performance for direct CO₂ electrolysis.