Roles of ion pairing on electroreduction of carbon dioxide based on imidazolium-based salts

•The significant electrocatalytic effects of imidazolium salts are due to a strong ion-pairing.•DFT calculation predicts the ion pair [BMIM+][CO2.−] conformation.•The extent of ion-pairing decreases with increasing the size of the alkyl substituent.

The roles of ion pairing on CO2 electroreduction involving imidazolium-based salts are explored on an Ag electrode in a DMF solution. The electroreductive behaviours of CO2 and the IR results establish the dominant role of the cation of imidazolium-based salts in CO2 electrocatalytic reduction process. Density functional theory (DFT) calculations predict that the ion pair formation is mainly driven by the attraction of the four nearby and positively charged hydrogen atoms which are at the C2, N1 and N3-positions of an imidazolium cation for the negatively charged oxygen atoms in the CO2.− species. The electrostatic interaction between an imidazolium cation and the CO2.− species decreases with increasing the size of the alkyl substituent at the N1-position of that imidazolium cation.

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