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

• Construction of a composite heterostructure of alkaline-earth metal compounds and Sr 2 Fe 1.5 Mo 0.5 O 6−δ (SFM) double perovskite oxides by alkaline-earth metal infiltration was proposed. • The heterostructure enriches the surface active sites and led to the expansion of the triple-phase boundary. • The infiltration of alkaline-earth metal improves the adsorption and activation process of CO 2 . • SFM-MCO 3 cathodes exhibit excellent electrochemical performance and the single cell reached the current density of 1.723 A cm −2 at 1.8 V and 800 °C. Solid oxide electrolysis cell (SOEC) can efficiently convert CO 2 to CO using renewable energy sources, which can alleviate the threatening impact of excessive CO 2 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 CO 2 reduction is crucial for realizing practical applications of SOEC. Herein, construction of a composite heterostructure of alkaline-earth metal compounds and Sr 2 Fe 1.5 Mo 0.5 O 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 CO 2 , and promotion of the formation of activated carbonate intermediates. The current density on the CaCO 3 -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.