Surface-Enhanced Raman Spectroscopic Evidence on the Origin of Selectivity in CO Electrocatalytic Reduction.

The electrocatalytic reduction of CO (COER) to liquid fuels is important for solving fossil fuel depletion. However, insufficient insight into the reaction mechanisms renders a lack of effective regulation of liquid product selectivity. Here, surface-enhanced Raman spectroscopy (SERS) empowered by C/C isotope exchange is applied to probing the COER process on nanoporous silver (np-Ag). Direct spectroscopic evidence of the preliminary intermediates, *COOH and *OCO, indicates that CO is coordinated to the catalyst diverse adsorption modes. Further, the relative Raman intensities of the above intermediates vary notably on np-Ag modified by Cu or Pd, and the liquid product selectivity also changes accordingly. Combined with density functional theory calculations, this study demonstrates that the CO adsorption configuration is a critical factor governing the reaction selectivity. Meanwhile, *COOH and *OCO are key targets in the initial stage regulating liquid product selectivity, which could facilitate future selective catalyst design.