In Situ Phase Separation into Coupled Interfaces for Promoting CO2 Electroreduction to Formate over a Wide Potential Window

Abstract Bimetallic sulfides are expected to realize efficient CO 2 electroreduction into formate over a wide potential window, however, they will undergo in situ structural evolution under the reaction conditions. Therefore, clarifying the structural evolution process, the real active site and the catalytic mechanism is significant. Here, taking Cu 2 SnS 3 as an example, we unveiled that Cu 2 SnS 3 occurred self‐adapted phase separation toward forming the stable SnO 2 @CuS and SnO 2 @Cu 2 O heterojunction during the electrochemical process. Calculations illustrated that the strongly coupled interfaces as real active sites driven the electron self‐flow from Sn 4+ to Cu + , thereby promoting the delocalized Sn sites to combine HCOO* with H*. Cu 2 SnS 3 nanosheets achieve over 83.4 % formate selectivity in a wide potential range from −0.6 V to −1.1 V. Our findings provide insight into the structural evolution process and performance‐enhanced origin of ternary sulfides under the CO 2 electroreduction.