Summary In this chapter we analyze the performance of C2 substituted imidazolium cations in promoting the electrochemical conversion of CO2. By using ATR-FTIR, and NMR spectroscopy of a white precipitate formed during the reaction, we demonstrate that reduction of CO2 takes place according to multiple pathways. On the one hand we provide evidence for the formation of CO and (bi)carbonate, formed by disproportionation of the CO2 dimer radical anion, and subsequent protonation of the carbonate anion. This is the dominant reaction, since gas chromatography showed a faradaic efficiency of ~80% towards CO. Interestingly, the formation of oxalate, formed by coupling of two CO2 - - radical anions – is also observed. Oxalate remains in solution, since this is not observed in the NMR analysis of the white precipitate, and therefore likely a minor pathway. Finally, using isotopic labeling for peak assignment – the formation of formate is spectroscopically observed, in agreement with the presence of this anion in the white precipitate – as determined by NMR analysis. This species is formed by protonation of the *CO2 - radical anion. This study shows that contrary to imidazolium cations allowing C2-H coordination to the *CO2 - - radical anion (in anhydrous conditions), providing 100% selectivity to the formation of CO, C2-substitution (and likely in the presence of residual water) lowers the reaction selectivity, opening upon channels to formation of other products such as formate and oxalate.
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