Direct Reduction of Carbon Dioxide to Formate in High-Gas-Capacity Ionic Liquids at Post-Transition-Metal Electrodes

• Published in: ChemSusChem 2014-01, Vol.7 (1), p.284-290
• Main Authors: Watkins, John D., Bocarsly, Andrew B.
• Format: Article
• Language: English
• Subjects: Acetates - chemistry; Carbon dioxide; Carbon Dioxide - chemistry; Carbon Sequestration; electrochemistry; Electrodes; Formates - chemistry; Gases; Imidazoles - chemistry; indium; ionic liquids; Ionic Liquids - chemistry; Ions; Liquids; Metals - chemistry; Oxidation-Reduction; reduction; Solvents
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.201300659

As an approach to combat the increasing emissions of carbon dioxide in the last 50 years, the sequestration of carbon dioxide gas in ionic liquids has become an attractive research area. Ionic liquids can be made that possess incredibly high molar absorption and specificity characteristics for carbon dioxide. Their high carbon dioxide solubility and specificity combined with their high inherent electrical conductivity also creates an ideal medium for the electrochemical reduction of carbon dioxide. Herein, a lesser studied ionic liquid, 1‐ethyl‐3‐methylimidazolium trifluoroacetate, was used as both an effective carbon dioxide capture material and subsequently as an electrochemical matrix with water for the direct reduction of carbon dioxide into formate at indium, tin, and lead electrodes in good yield (ca. 3 mg h−1 cm−2). It's the water: Water enhances CO2 reduction rates when using a mixed ionic liquid (EMIM TFA)/water matrix to facilitate the conversion of CO2 into formate on indium electrodes. Addition of greater amounts of water lowers the overpotential for the reduction of CO2 as well as increases the rate of CO2 reduction as shown by the linear sweep voltammograms (see picture).