at 2252 cm-1 and 2292 cm-1 within the FTIR spectra of MeCN (as presented in Supporting Information Section IV) further corroborate these assignments. Peaks observed at 2850 cm-1, 2919 cm-1, and 2950 cm-1 can be attributed to the imidazolium cation, as discussed in the context of spectra recorded under an Ar atmosphere. These findings suggest that during CO2 reduction, imidazolium cations maintain their concentration within the electronic double layer. Simultaneously, CO2 likely replaces acetonitrile molecules to engage in the catalytic reaction. In other words, if CO2 were to displace imidazolium molecules, we would expect to observe negative bands corresponding to the imidazolium cation. This further implies that imidazolium cations are less likely to be specifically adsorbed at the catalytic sites and are rather present within the electronic double layer. In agreement with the gas phase analysis, the formation of CO is readily observed in our spectra. The recent work by Wang et al. 127 has demonstrated that CO adsorption on Au/TiO2 generates a distinct peak at approximately 2100 cm-1. We also detect a positive band at 2100 cm-1 that persists during CO2 reduction (as shown in Figure 6.2). Tao et al. 128 have postulated that a band at 2100 cm-1 could be attributed to CO adsorbed on single-fold top sites of the Au electrode. They proposed that CO adsorption on twofold or multifold Au sites would lead to the observation of bands at lower wavenumbers, specifically at 2000 cm-1 and 1940 cm-1, respectively. This observation substantiates our suggestion that single-fold CO adsorption on Au sites is taking place. As previously stated for the NMR analysis, to facilitate the identification of other peaks, we conducted the synthesis of various imidazolium complexes, which included (BMMIM)2 CO3, (BMMIM)2 C2O4, BMMIM HCO3, and BMMIM HCOO. Notably, BMMIM HCO3 and (BMMIM)2 C2O4 were observed as white solids, while imidazolium formate and imidazolium carbonate exhibited a distinct behavior, existing as viscous liquids post-anion exchange. Particularly noteworthy is the distinctive change in color observed with imidazolium carbonate.
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