SrO-layer insertion in Ruddlesden-Popper Sn-based perovskite enables efficient CO electroreduction towards formate.

Tin (Sn)-based oxides have been proved to be promising catalysts for the electrochemical CO reduction reaction (CORR) to formate (HCOO). However, their performance is limited by their reductive transformation into metallic derivatives during the cathodic reaction. This paper describes the catalytic chemistry of a SrSnO electrocatalyst with a Ruddlesden-Popper (RP) perovskite structure for the CORR. The SrSnO electrocatalyst exhibits a faradaic efficiency of 83.7% for HCOO at -1.08 V the reversible hydrogen electrode with stability for over 24 h. The insertion of the SrO-layer in the RP structure of SrSnO leads to a change in the filling status of the anti-bonding orbitals of the Sn active sites, which optimizes the binding energy of *OCHO and results in high selectivity for HCOO. At the same time, the interlayer interaction between interfacial octahedral layers and the SrO-layers makes the crystalline structure stable during the CORR. This study would provide fundamental guidelines for the exploration of perovskite-based electrocatalysts to achieve consistently high selectivity in the CORR.