Medium-entropy strategy to inhibit the surface Sr segregation and enhance the stability of Sr 2 Fe 1.3 Mo 0.5 O 6-δ cathode for CO2 direct electrolysis

Solid oxide electrolysis cell (SOEC) is a promising solid-state electrochemical device that can convert CO2 into CO with high efficiency. However, the poor catalytic activity and Sr segregation of the cathode diminish the electrode reaction, hindering the large-scale application. Herein, a medium-entropy strategy is proposed to suppress the Sr enrichment while enhancing the catalytic activity for CO2. The surface Sr content on Sr 2 Fe 1.2 Ni 0.1 Cu 0.1- Co 0.1 Mo 0.5 O 6-s (SFNCCM) is significantly reduced after the Ni, Cu, and Co co-doping at Fe-site. Moreover, the oxygen surface exchange and bulk diffusion coefficient at 800 degrees C for SFNCCM oxide reach 2.42 x 10-4 cm2 s-1 and 2.28 x 10-5 cm2 s- 1 , which are 1.35 and 1.39 times higher than parent Sr2Fe1.5Mo0.5O6-s(SFM) oxide. At 850 degrees C and 1.5 V, single with SFNCCM-Sm0.2Ce0.8O6-s(SDC) composite exhibits a current density of 2.22 A cm-2 with good stability for up to 100 h. The results suggest that the medium-entropy strategy is a promising method to inhibit Sr segregation and enhance the performance of CO2 direct electrolysis.