electrostatic interactions. The argument for CO2 stabilization through hydrogen bonding with imidazolium cations in anhydrous media, as discussed in this thesis, shares similarities with the role of alkali metal cations in aqueous media. The discrepancy in the role of alkali cations between aqueous and non-aqueous media can be explained by considering the role of solvation in acetonitrile compared to water. According to prior research findings, in aprotic solvents, carbonate species formed during electrochemical reduction tend to precipitate in the presence of alkali metal cations. This phenomenon leads to the passivation of the active electrode surface and the subsequent halt of CO2 reduction 140-141. Setterfield-Price and Dryfe 140 demonstrated the presence of deactivating inorganic salts (LiOCO2 and Li2CO3 were detected via Raman spectroscopy) on the electrode surface (Au and Pt) after CO2 reduction with 0.1 M LiBF4 in NMP solvent. The coupling of carbonate species occurs following the second electron transfer, during which alkali metals with higher charge density than organic cations form insoluble inorganic salts. The zoomed-in version of the cyclic voltammetry results from Figure 7.2 for K NTf2 and Cs NTf2 electrolytes (Figure 7.4) reveals an early mass-diffusion limited current reached at negative potentials around -1.8 V (vs. Ag/Ag+). This negative peak current can be interpreted as an indirect sign of the formation of a passivation layer over the electrode surface upon CO2 reduction. Kash et al.141, have demonstrated a potential solution to this issue by introducing acids to aprotic media, such as methanesulfonic acid to dimethyl sulfoxide. This approach led to the formation of CO2 reduction products with up to 80% faradaic efficiency. Their study highlights the importance of considering alternative electrolyte systems and acid additives to improve the efficiency of CO2 reduction in aprotic solvents when alkali metals are used as electrolyte. However, it is important to note that introducing acids to the aprotic solvents alters the composition of the electrolyte. This makes it challenging to directly compare the performance of alkali metal cations and imidazolium cations for non-aqueous CO2 reduction.
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