Introduction In Chapters 3 and 4, we extensively discussed the primary mechanism behind the promotional impact of C2-hydrogenated imidazolium cations. It was concluded that the C2-proton of the cation plays a crucial role in stabilizing the negatively charged intermediate (*CO2 -). We also demonstrated a higher overpotential recorded with C2-methylated imidazolium compared to C2-hydrogenated cations, signifying reduced co-catalytic performance for the latter. While we discussed 100% faradaic efficiency (FE) for CO formation with C2-hydrogenated cations, we did not extensively discuss the reaction course and selectivity for the C2-methylated cations. Indeed, lower kinetic improvements observed for these cations compared to C2-protonated cations might also entail different selectivity and reaction courses in non-aqueous media. The most referenced work on C2-substituted imidazolium for electrochemical CO2 reduction in acetonitrile is Lau et al.'s study8, which explored modulating C4- and C5-proton donation through the impact of C2-substituents for CO2 reduction over an Ag electrode. While they mostly reported the formation of CO, information on anhydrous conditions and water content was lacking in their study. Additionally, The use of Ag/AgCl as a supporting salt in the reference capillary in that work is not consistent with our protocol and findings in Chapter 2, which demonstrated the significant potential impact of Ag particles in the system in the presence of imidazolium cations. Thus, in this chapter, we aim to gain more insight into the performance of C2-methylated imidazolium using ATR-FTIR studies in combination with our established electrochemical support experiments and ex-situ FTIR and NMR analysis. The chosen imidazolium cation is 1-butyl, 2,3-dimethyl imidazolium (BMMIM), which is commercially available, and NTf2 is the common anion.
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