Unlocking the Potential of A-Site Ca-Doped LaCoFeO: A Redox-Stable Cathode Material Enabling High Current Density in Direct CO Electrolysis.

Massive carbon dioxide (CO) 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 CO into valuable chemicals using renewable energy sources. However, Sr-containing cathode materials face the challenge of Sr carbonation during CO electrolysis, which greatly affects the energy conversion efficiency and long-term stability. Thus, A-site Ca-doped LaCaCoFeO (0.2 ≤ ≤ 0.6) oxides are developed for direct CO conversion to carbon monoxide (CO) in an intermediate-temperature SOEC (IT-SOEC). With a polarization resistance as low as 0.18 Ω cm in pure CO atmosphere, a remarkable current density of 2.24 A cm was achieved at 1.5 V with LaCaCoFeO (LCCF64) as the cathode in LaSrGaMgO (LSGM) electrolyte (300 μm) supported electrolysis cells using LaSrCoFeO (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 at 1.5 V at 800 °C. In addition, stable cell performance has been achieved on direct CO electrolysis at an applied constant current of 0.5 A cm at 800 °C. The easily removable carbonate intermediate produced during direct CO 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 exsolved Co/CoFe nanoparticles and the additional oxygen vacancies originated from the CaFeO phase synergistically providing active sites for CO adsorption and electrolysis. This study offers a novel approach to design catalysts with high performance for direct CO electrolysis.