The electrochemical reduction of CO₂ on a copper electrode in 1-n -butyl-3-methyl imidazolium tetrafluoroborate (BMI.BF₄ ) monitored by surface-enhanced Raman scattering (SERS)

Abstract

The electrochemical conversion of CO 2 into value-added products using room temperature ionic liquids as solvent/electrolyte has been proposed as an alternative to minimize the environmental effects of CO 2 emissions. A key issue in the design of electrochemical systems for the reduction of CO 2 is the in situ identification of intermediate surface species as well as reaction products. Copper electrodes, besides being used as cathodes in the electrochemical reduction of CO 2 , present surface-enhanced Raman scattering (SERS) when properly activated. In this sense, the electrochemical reduction of CO 2 over a copper electrode in the room temperature ionic liquids 1-n-butyl-3-methyl imidazolium tetrafluoroborate (BMI.BF 4 ) was investigated by cyclic voltammetry and by in situ SERS. The cyclic voltammetries have shown that the presence of CO 2 on the BMI.BF 4 anticipates the reduction of BMI + to the corresponding carbene. Fourier-transform-SERS spectra excited at 1064 nm and SERS spectra excited at 632.8 nm have shown vibrational signals from adsorbed CO. These SERS results indicated that CO adsorbs on the copper surface at two different surface sites. The observation of a 2275 cm À1 vibration in the SERS spectra also confirmed the presence of chemically adsorbed CO 2 . Other products of CO 2 reduction in BMI.BF 4 , besides CO, were identified, including BMI carbene and the BMI-CO 2 adduct. The SERS results also suggest that the presence of a thin film of Cu 2 O on the copper surface anticipates the reduction of CO 2 to CO, an important component of syngas.

On the origin of the elusive first intermediate of CO 2 electroreduction

“…46 and SI Appendix in ref. 47). The 360-cm −1 peak is not observed even when the relative νCO intensity is higher by a factor of 3 (SI Appendix, Fig.…”

Electrocatalytic Reduction of CO2 in Ionic Liquid-Based Electrolytes

“…(i) Development of ILs are able to co-catalyze CO 2 reduction to form products beyond CO. Most of the currently developed catalysts can only reduce CO 2 to the twoelectron-transfer product CO, even on copper [90], which is able to produce hydrocarbons and alcohols at appreciable selectivity in aqueous media [13,91]. This indicates that the reaction pathways in IL-based electrolyte are different from those in aqueous media.…”

Recent advances in linear and non‐linear Raman spectroscopy. Part XI

“…Santos et al monitored the electrochemical reduction of CO 2 on a copper electrode in 1‐ n ‐butyl‐3‐methyl imidazolium tetrafluoroborate (BMI.BF 4 ) using SERS. They found that the SERS results suggest that the presence of a thin film of Cu 2 O on the copper surface anticipates the reduction of CO 2 to CO, an important component of syngas . Schuetz and Schluecker report the use of spectral multiplexing with six silica‐encapsulated SERS labels as an approach towards quantitative multicolour nanodiagnostics.…”