Artificial Photosynthesis: Conversion of CO2 at Low Temperature and Potential Using Ionic Liquids
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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 capture atmospheric carbon dioxide and reduce it to CO, a precursor for fuel synthesis. Rather than traditional solvents such as water, sulfuric acid, or acetonitrile, room temperature ionic liquids (RTIL's) will be employed as the solvent for CO2 capture and reduction. RTIL's have many favorable properties such as extended electrochemical windows, high thermal stability, high electrical conductivity, and a 100+ fold increase in carbon dioxide solubility compared to water. Additionally, the absence water can increase the efficiency of CO production by eliminating the hydrogen and oxygen evolution reactions. Cyclic voltammetry has shown the catalytic reduction of CO2 at the Pt and Pt/Ru surface in imidazolium based ionic liquids such as EMIM BF4, BMIM BF4 and EMIM NTF. Cathodic shoulders correlating to the reduction of CO2 are found at ca. -0.5V vs. SHE, which is over half a volt less negative than previously reported in aqueous solvents, and 400mV less negative than reported in other non-aqueous solvents. CO stripping experiments and Broadband Sum Frequency Generation Spectroscopy (BB-SFG) has qualitatively confirmed that at least one of the reduction products is CO. Because this novel setup has eliminated much of the overpotential traditionally associated with CO2 reduction, this process can take place at much higher efficiencies, as well as re-open the door for investigating non-precious metal electrodes originally eliminated due to their low efficiency in the presence of water.