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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.
Xu et al. (Thu,) studied this question.