Cation‐Radius‐Controlled Sn−O Bond Length Boosting CO2 Electroreduction over Sn‐Based Perovskite Oxides

Abstract Despite the intriguing potential shown by Sn‐based perovskite oxides in CO 2 electroreduction (CO 2 RR), the rational optimization of their CO 2 RR properties is still lacking. Here we report an effective strategy to promote CO 2 ‐to‐HCOOH conversion of Sn‐based perovskite oxides by A‐site‐radius‐controlled Sn−O bond lengths. For the proof‐of‐concept examples of Ba 1−x Sr x SnO 3 , as the A‐site cation average radii decrease from 1.61 to 1.44 Å, their Sn−O bonds are precisely shortened from 2.06 to 2.02 Å. Our CO 2 RR measurements show that the activity and selectivity of these samples for HCOOH production exhibit volcano‐type trends with the Sn−O bond lengths. Among these samples, the Ba 0.5 Sr 0.5 SnO 3 features the optimal activity (753.6 mA ⋅ cm −2 ) and selectivity (90.9 %) for HCOOH, better than those of the reported Sn‐based oxides. Such optimized CO 2 RR properties could be attributed to favorable merits conferred by the precisely controlled Sn−O bond lengths, e.g., the regulated band center, modulated adsorption/activation of intermediates, and reduced energy barrier for *OCHO formation. This work brings a new avenue for rational design of advanced Sn‐based perovskite oxides toward CO 2 RR.