In Situ Dynamic Construction of a Copper Tin Sulfide Catalyst for High-Performance Electrochemical CO₂Conversion to Formate

Electrochemical reduction of CO₂to produce fuels and chemicals is one of the most valuable approaches to achieve a carbon-neutral cycle. Recently, a diversity of catalysts have been developed to improve their intrinsic activity and efficiency. However, the dynamic evolution process and the in situ construction behavior of electrocatalysts under the working conditions are typically ignored. Here, we fully reveal the dynamic reduction process and phase transformation of a copper tin sulfide catalyst reconstructed by in situ reduction of the precatalyst Cu₂SnS₃and CuS during electrochemical CO₂reduction. Furthermore, the reconstructed catalyst reaches an outstanding electrochemical CO₂-to-formate conversion with a high Faradaic efficiency of 96.4% at an impressive production rate of 124889.9 μmol mg^-1h^-1under a partial current density of -241 mA cm^-2(-669.4 A g^-1) in a flow-cell reactor. Theoretical calculations further demonstrate the strong charge interaction between the adsorbate and substrate to accelerate the charge transfer and decrease the formation energies of OCHO∗ and HCOOH∗ intermediates in the pathway of CO₂to HCOOH, resulting in high selectivity for formate on the surface of the copper tin sulfide catalyst. This work paves the way for revealing the in situ dynamic process of the reconstructed catalyst and designing optimal catalysts with high catalytic activity and selectivity.