CO₂ Electroreduction on Silver Foams Modified by Ionic Liquids with Different Cation Side Chain Length

Ionic liquids (ILs) are capable of tuning the kinetics of electroreduction processes by modifying a catalyst interface. In this work, a group of hydrophobic imidazolium-based ILs were immobilized on Ag foams by using a procedure known as “solid catalyst with ionic liquid layer” (SCILL). The derived electrocatalysts demonstrated altered selectivity and CO production rates for the electrochemical reduction of CO2 compared to the unmodified Ag foam. The activity change caused by the IL was dependent on the length of the N-alkyl substituent. The rate of CO production is optimized at moderate chain length and IL loadings. The observed trends are attributed to a local enrichment of CO2-based species in the proximity of the catalyst and a modification of the environment of its active sites. On the contrary, high loadings or long IL chains render the surface inaccessible and favor the hydrogen evolution reaction.