Constructing perovskite/alkaline-earth metal composite heterostructure by infiltration to revitalize CO₂ electrolysis

Solid oxide electrolysis cell (SOEC) can efficiently convert CO₂ to CO using renewable energy sources, which can alleviate the threatening impact of excessive CO₂ emissions on the human life and environment. Moreover, it also realizes chemical storage of available electricity to ease the energy consumption crisis. Designing cathode materials with abundant active sites and high-efficiency electrochemical catalytic activity toward CO₂ reduction is crucial for realizing practical applications of SOEC. Herein, construction of a composite heterostructure of alkaline-earth metal compounds and Sr₂Fe_1.5Mo_0.5O_6−δ (SFM) double perovskite oxides by alkaline-earth metal infiltration was proposed. This strategy enriched the reactive sites and led to the expansion of the triple-phase boundary, thereby effectively improving the electrochemical performance of SOEC. The experimental results show that the infiltration of alkaline-earth metal led to significant increase in the surface active sites, improvement in the adsorption and activation process of CO₂, and promotion of the formation of activated carbonate intermediates. The current density on the CaCO₃-infiltrated SFM cathode reached 1.723 A cm⁻², while the current density on the SFM cathode could only reach 1.117 A cm⁻² at 1.8 V and 800 °C. The alkaline-earth metal infiltration strategy not only improves the electrochemical performance, but also maintains excellent stability after 100 h of operation at high temperature and 12 redox cycles. All these results indicate that the construction of heterostructure through alkaline-earth metal infiltration provides an effectual strategy for improving the electrochemical performance of SOEC.