Enhancing Selective Electrochemical CO₂ Reduction by In Situ Constructing Tensile-Strained Cu Catalysts

Heteroatom-doped Cu-based catalysts have been found to show not only enhanced activity of electrochemical CO2 reduction reaction (CO2RR) but also the possibility to tune the selectivity of CO2RR. However, the complex and variable nature of Cu-based materials renders it difficult to elucidate the origin of the improved performance, which further hinders the rational design of catalysts. Here, we demonstrate that the activity and selectivity of CO2RR can be tuned by manipulating the lattice strain of Cu-based catalysts. The combined operando and ex situ spectroscopic characterizations reveal that the initial compressively strained Sn-doped CuO catalysts could be converted to tensile-strained Sn/Cu alloy catalysts under reaction conditions. In situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEITAS) and theoretical calculations further show that the tensile-strained Sn/Cu alloy catalysts favor CO formation due to the preponderant adsorption of *CO and much lower adsorption free energies of *COOH, thus effectively suppressing the dimerization process and the production of HCOOH and H2. This work provides a strategy to tune the CO2RR performance of Cu-based catalysts by manipulating the lattice strain.