Unlocking the Potential of A-Site Ca-Doped LaCo 0.2 Fe 0.8 O 3-δ : A Redox-Stable Cathode Material Enabling High Current Density in Direct CO 2 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.