SrO-layer insertion in Ruddlesden–Popper Sn-based perovskite enables efficient CO2 electroreduction towards formate

Tin (Sn)-based oxides have been proved to be promising catalysts for the electrochemical CO2 reduction reaction (CO2RR) 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 Sr2SnO4 electrocatalyst with a Ruddlesden-Popper (RP) perovskite structure for the CO2RR. The Sr2SnO4 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 Sr2SnO4 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 CO2RR. This study would provide fundamental guidelines for the exploration of perovskite-based electrocatalysts to achieve consistently high selectivity in the CO2RR.