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

Despite the intriguing potential shown by Sn‐based perovskite oxides in CO2 electroreduction (CO2RR), the rational optimization of their CO2RR properties is still lacking. Here we report an effective strategy to promote CO2‐to‐HCOOH conversion of Sn‐based perovskite oxides by A‐site‐radius‐controlled Sn−O bond lengths. For the proof‐of‐concept examples of Ba1−xSrxSnO3, 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 CO2RR 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 Ba0.5Sr0.5SnO3 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 CO2RR 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 CO2RR. [ABSTRACT FROM AUTHOR]