In Situ Phase Separation into Coupled Interfaces for Promoting CO 2 Electroreduction to Formate over a Wide Potential Window

Bimetallic sulfides are expected to realize efficient CO2 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 Cu2SnS3 as an example, we unveiled that Cu2SnS3 occurred self-adapted phase separation toward forming the stable SnO2@CuS and SnO2@Cu2O heterojunction during the electrochemical process. Calculations illustrated that the strongly coupled interfaces as real active sites driven the electron self-flow from Sn4+ to Cu+, thereby promoting the delocalized Sn sites to combine HCOO* with H*. Cu2SnS3 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 CO2 electroreduction.