Ionic Liquid-Mediated Selective Conversion of CO₂ to CO at Low Overpotentials

• Published in: Science (American Association for the Advancement of Science) 2011-11, Vol.334 (6056), p.643-644
• Main Authors: Rosen, Brian A., Salehi-Khojin, Amin, Thorson, Michael R., Zhu, Wei, Whipple, Devin T., Kenis, Paul J. A., Masel, Richard I.
• Format: Article
• Language: English
• Subjects: Anodes; Biophysics; Carbon dioxide; Carbon Dioxide - chemistry; Carbon monoxide; Carbon Monoxide - chemistry; Catalysis; Cathodes; Chemistry; Complexation; Conversion; Dioxides; Electric potential; Electrochemical cells; Electrochemistry; Electrodes: preparations and properties; Electrolytes; Energy conversion efficiency; Energy efficiency; Exact sciences and technology; General and physical chemistry; Imidazoles - chemistry; Imides - chemistry; Ionic liquids; Ions; Other electrodes; Photosynthesis; Reduction (electrolytic); Silver; Surface areas; Voltage; Water
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.1209786

Electroreduction of carbon dioxide (CO₂)—a key component of artificial photosynthesis—has largely been stymied by the impractically high overpotentials necessary to drive the process. We report an electrocatalytic system that reduces CO₂ to carbon monoxide (CO) at overpotentials below 0.2 volt. The system relies on an ionic liquid electrolyte to lower the energy of the (CO₂)⁻ intermediate, most likely by complexation, and thereby lower the initial reduction barrier. The silver cathode then catalyzes formation of the final products. Formation of gaseous CO is first observed at an applied voltage of 1.5 volts, just slightly above the minimum (i.e., equilibrium) voltage of 1.33 volts. The system continued producing CO for at least 7 hours at Faradaic efficiencies greater than 96%.