the relative concentrations when compared to the bulk phase—an occurrence frequently observed at negatively charged electrodes. The minor positive feature observed around ~2253 cm-1 can be attributed to the CN stretch mode of acetonitrile molecules 121. This band is similarly present in the FTIR spectra of pure acetonitrile (as depicted in Supporting Information Figure S6.6). Moreover, an additional positive feature appears at 2080 cm-1, which is not evident in the FTIR analysis of bulk acetonitrile. Acetonitrile has the capacity to interact with negatively charged surfaces122, leading to the generation of adsorbed acetonitrile or even carbanion CH2CN- species. These species might exhibit CN vibrations at wavenumbers lower than those of free acetonitrile molecules 119, 123. The negative band at 1658 cm-1 can be attributed to the bending mode of residual water molecules that have undergone chemisorption on the surface 121, 124. It's important to note that the bending frequency of water in its liquid state is typically reported as 1640 cm-1. The 18 cm-1 blue shift observed could be attributed to the interaction with the negatively polarized Au film electrode, a reasoning also supported by Faguy et al. 121. It is pertinent to mention that the ATR-FTIR experiment in this study deviates slightly from the protocol detailed in Chapter 2. This deviation is due to the specific apparatus used and the challenges encountered in maintaining stringent anhydrous conditions. Consequently, a greater concentration of residual water is to be expected compared to experiments outlined in other chapters. However, unlike the findings of Figueiredo et al. 21 , we lack any indication of water reduction followed by the subsequent decomposition of acetonitrile into acetamide. This disparity could potentially be attributed to factors such as the inhibitory influence of the imidazolium cation 125, the meticulous control we have exercised over our water system, and the characteristics of the Au electrode (as discussed in Chapter 5).
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