SrO-layer insertion in Ruddlesden-Popper Sn-based perovskite enables efficient CO 2 electroreduction towards formate.

Tin (Sn)-based oxides have been proved to be promising catalysts for the electrochemical CO 2 reduction reaction (CO 2 RR) 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 Sr 2 SnO 4 electrocatalyst with a Ruddlesden-Popper (RP) perovskite structure for the CO 2 RR. The Sr 2 SnO 4 electrocatalyst exhibits a faradaic efficiency of 83.7% for HCOO - at -1.08 V vs. the reversible hydrogen electrode with stability for over 24 h. The insertion of the SrO-layer in the RP structure of Sr 2 SnO 4 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 CO 2 RR. This study would provide fundamental guidelines for the exploration of perovskite-based electrocatalysts to achieve consistently high selectivity in the CO 2 RR.