Tuning the Selectivity of Liquid Products of CO₂RR by Cu–Ag Alloying

The combination of Cu and Ag presents a promising way to steer the CO₂ reduction products through regulating the surface active sites. However, the difficulty in forming the CuAg alloy with a controllable atomic ratio impedes the in-depth understanding of the structure-activity relationship of CuAg catalysts. Herein, we use E-beam evaporation to synthesize a series of CuAg films with uniform distribution and controllable stoichiometry to reveal the real reaction mechanism on CuAg for the electrochemical CO₂ reduction process. Compared with Cu, the Cu1-xAgx (x = 0.05-0.2) alloy showed an apparent suppression of HCOOH and the ratio between C₂ liquid products (e.g., ethanol and acetate) and C₁ liquid product (HCOOH) is also increased. Operando synchrotron radiation Fourier transform infrared spectroscopy results suggest that the introduction of Ag into the Cu phase can significantly strengthen the absorbed *CO and *OCCO intermediates and suppress the O-C-O intermediates. This research provides a reliable way to inhibit the generation of HCOOH and enhance the production of liquid C₂ products during CO₂RR and presents a guideline for the future manipulation of copper catalysts by alloying.