Conclusion This study demonstrated a correlation between the C2-H acidity of imidazolium cations and the achievable current density in the reduction of CO2 under anhydrous conditions. This correlation was established by modifying the functionality of the molecule at the N1 and N3 positions. The inverse kinetic isotope effect and Tafel analysis showed that the rate-determining step involves a concerted coupled electron-proton transfer with a partial proton transfer, which leaves room for even further optimizing the molecular structure. What we have not assessed in the present study, is the interaction of the conjugated base of the imidazolium cation (carbene) with the electrode. N-Heterocyclic carbenes (NHCs) readily bind transition metals by -donation5, and recently their great affinity for electrode surfaces such as Au has been shown76. The relevance of such interaction for performance in the electrochemical reduction of CO2 needs to be assessed for electrodes of different binding energies. Figure 3.5. (a) DFT calculation for a CEPT rate-determining step for MM co-catalyzed CO2 reduction in anhydrous acetonitrile. (b) LSVs recorded using Au rotating disk electrode (2000 rpm) withMM and deuterated MM in CO2 saturated acetonitrile showing an experimental inverse kinetic isotope effect, for quantification of iKIE see Supporting Information Figure S3.5. a b
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