Electrochemical reduction of CO2 on silver as probed by surface‐enhanced Raman scattering

Abstract

AbstractSurface‐enhanced Raman scattering (SERS) spectroscopy was used to explore the electrochemical reduction of CO2 at a polycrystalline Ag electrode in KHCO3 aqueous solution saturated with CO2 at room temperature. Raman scattering from the oxidation‐reduction cycled Ag electrode suggests the formation of CO and HCOOH by CO2 reduction. At an electrode potential of 0.08 V (vs. Ag/AgCl), adsorbed CO gives rise to a C‐O stretch band at 2128 cm−1. This band decreases in intensity and shifts to higher wavenumber with an increase of negative potential in the range from 0.0 to − 0.24 V. A different potential dependence is observed for the C‐H stretch mode of adsorbed HCOO− (2870 cm−1 at − 0.8 V). The O‐C‐O antisymmetric and symmetric stretch modes of HCOO− observed at near 1550 and 1350 cm−1 decrease in intensity with increasing negative potential, presenting a striking contrast to the C‐H stretch mode. The SERS experiment with a CO2‐saturated KHCO3D2O solution is also described and discussed.