(17a) CO2 Reduction in EMIM BF4 – H2SO4 and EMIM BF4 – H2O Mixtures On Silver and Platinum Cathodes

Alternative energy and climate change are among the largest concerns facing scientists and engineers at the start of the twenty-first century. The focus of this research is the design of a system that can efficiently convert carbon dioxide and water to carbon monoxide and hydrogen, a precursor for gasoline synthesis. Rather than traditional electrolyte solvents such as water, sulfuric acid, or acetonitrile, room temperature ionic liquid (RTIL) mixtures will be employed as the electrolyte solvent for CO2 capture and reduction. RTIL's have many favorable properties such as extended electrochemical windows, high thermal stability, high electrical conductivity, and in some cases, 100+ fold increase in carbon dioxide solubility compared to water. We have shown that in an 18 mol% EMIM BF4/water electrolyte, CO2 can be converted to CO with 95% selectivity at only 150mV overpotential on the cell.  We find that the peak in CO selectivity in these ionic liquid/aqueous mixtures occurs at intermediate volume fractions, and attribute this to the competing effects of transport and stability which change as the ionic liquids are diluted. By varying the ratio of EMIM BF4 with water or acid (i.e. sulfuric or perchloric acid), the ratio of CO:H2 in the gas outlet stream of the electrolyzer can be tailored for a wide variety of needs.