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 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 Cu₂ SnS₃ as an example, we unveiled that Cu₂ SnS₃ occurred self-adapted phase separation toward forming the stable SnO₂ @CuS and SnO₂ @Cu₂ O 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*. Cu₂ SnS₃ 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.

Keywords: CO2 electroreduciton; Cu-Sn catalyst; delocalized electron states; heterojunctions; phase separation.