Atomistic Insights into Medium-Entropy Perovskites for Efficient and Robust CO 2 Electrolysis.

Solid oxide electrolysis cells (SOECs) show great promise in converting CO 2 to valuable products. However, their practicality for the CO 2 reduction reaction (CO 2 RR) is restricted by sluggish kinetics and limited durability. Herein, we propose a novel medium-entropy perovskite, Sr 2 (Fe 1.0 Ti 0.25 Cr 0.25 Mn 0.25 Mo 0.25 )O 6-δ (SFTCMM), as a potential electrode material for symmetrical SOEC toward CO 2 RR. Experimental and theoretical results unveil that the configuration entropy of SFTCMM perovskites contributes to the strengthened metal 3d-O 2p hybridization and the reduced O 2p bond center. This variation of electronic structure benefits oxygen vacancy creation and diffusion as well as CO 2 adsorption and activation and ultimately accelerates CO 2 RR and oxygen electrocatalysis kinetics. Notably, the SFTCMM-based symmetrical SOEC delivers an excellent current density of 1.50 A cm -2 at 800 °C and 1.5 V, surpassing the prototype Sr 2 Fe 1.5 Mo 0.5 O 6-δ (SFM, 1.04 A cm -2 ) and most of the state-of-the-art electrodes for symmetrical SOECs. Moreover, the SFTCMM-based symmetrical SOEC demonstrates stable CO 2 RR operation for 160 h.