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

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Science  29 Sep 2011:
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. Here, we report an electrocatalytic system that reduces CO2 to carbon monoxide (CO) at overpotentials below 0.2 volts (V). 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. Then the silver cathode catalyzes formation of the final products. Formation of gaseous CO is first observed at an applied voltage of 1.5 V, just slightly above the minimum (i.e., equilibrium) voltage of 1.33 V. The system continued producing CO for at least 7 hours at Faradaic efficiencies over 96%.