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

Abstract

Surfaceenhanced Raman scattering (SERS) spectroscopy was used to explore the electrochemical reduction of CO, at a polycrystalline Ag electrode in KHCO, aqueous solution saturated with CO, at room temperature. Raman scattering from the oxidatioweduction cycled Ag electrode suggests the formation of CO and HCOOH by CO, 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-'. 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-' at -0.8 V). The O -C a antisymmetric and symmetric stretch modes of HCOO-observed at near 1550 and 1350 cm-' decrease in intensity with increasing negative potential, presenting a striking contrast to the C-H stretch mode. The SERS experiment with a C0,-saturated KHC0,-D,O solution is also described and discussed.

Spectroscopic evidences of the presence of hydrogenated species on the surface of copper during CO2 electroreduction at low cathodic potentials

“…Spectroelectrochemical techniques can be very useful to gain further insights into the formed adsorbates, and consequently to increase the understanding about the mechanisms involved in the reaction. Then, several works using spectroelectrochemical techniques to study the CO 2 electroreduction can be found in the literature [7][8][9][10][11][12]. In these works, the presence of bands of adsorbed CO has been shown (CO stretching at approximately 2040-2080 cm À1 , Cu-CO stretching at 358 cm À1 , and Cu-CO frustrated rotation at 280 cm À1 ) [8][9][10][11].…”

“…In this sense, spectroelectrochemical vibrational techniques such as Fourier transform infrared absorption spectroscopy (FTIRAS) [5] and surface enhanced Raman scattering (SERS) [6] can provide useful information about the possible adsorbed reaction intermediates, and hence aid to delineate a better view concerning the mechanisms involved. Several authors have used these techniques to study the CO 2 electroreduction [7][8][9][10][11][12].…”

A review of the aqueous electrochemical reduction of CO2 to hydrocarbons at copper

“…Others have reported similar vibrations during the oxidation of formate using silver, which they attributed to adsorbed carboxy species [36]. Adsorbed formate on silver is also reported to give vibrations at 1550 cm À1 (O-C-O antisymmetric stretch) and 1350 cm À1 (O-C-O symmetric stretch) [37], and at 1560 and 1360 cm À1 in UHV [38]. Prof. Hori's group has recorded a vibration at 1545 cm À1 in 0.2 M K 2 CO 3 solution assigned to adsorbed carbonate [30].…”

In Situ Surface-Enhanced Raman Spectroscopy of the Electrochemical Reduction of Carbon Dioxide on Silver with 3,5-Diamino-1,2,4-Triazole

“…10B shows that in Ar, a Ag-N stretching mode is also observed with potential-dependence very similar to those of peaks 14, 15, and 16. Figure 11: Normalized, baseline-corrected intensity as a function of cathodic potential during CO 2 reduction for the non-coordinated CO stretching band (10) and four bands related to surface-bound DAT (14,15,16,17). Figure 11 shows the potential dependence of the normalized, baseline-corrected peak intensity for the stretching frequency of the non-coordinated CO peak at 2099 cm -1 that appears when DAT is added for CO 2 reduction.…”

“…Overlaid in this spectrum is the potential dependence of the four bands (14,15,16,17) associated with DAT retention on the Ag surface. The figure shows that modes associated with DAT (or possibly its degradation product) are present on the electrode surface at the same potentials where the non-coordinated CO band is present.…”