Electrochemical reduction of CO₂ at metal electrodes in a distillable ionic liquid

The electroreduction of CO₂ in the distillable ionic liquid dimethylammonium dimethylcarbamate (dimcarb) has been investigated with 17 metal electrodes. Analysis of the electrolysis products reveals that aluminum, bismuth, lead, copper, nickel, palladium, platinum, iron, molybdenum, titanium and zirconium electroreduce the available protons in dimcarb to hydrogen rather than reducing CO₂. Conversely, indium, tin, zinc, silver and gold are able to catalyze the reduction of CO₂ to predominantly carbon monoxide (CO) and to a lesser extent, formate ([HCOO]⁻). In all cases, the applied potential was found to have a minimal influence on the distribution of the reduction products. Overall, indium was found to be the best electrocatalyst for CO₂ reduction in dimcarb, with faradaic efficiencies of approximately 45 % and 40 % for the generation of CO and [HCOO]⁻, respectively, at a potential of −1.34 V versus Cc^+/0 (Cc⁺=cobaltocenium) employing a dimethylamine to CO₂ ratio of less than 1.8:1.