(726b) Electrochemical Reduction of CO2 on Cu Catalysts in a Diluted Ionic Liquid/Water Mixture

The growing atmospheric concentration of CO₂, a greenhouse gas, results in global warming and climate change. Electroreduction of CO₂ is one of the promising methods to convert waste CO₂ to valuable chemicals and fuels. Among the metallic catalysts used in CO₂ electroreduction, copper is known to produce hydrocarbons. However, CO₂ electroreduction on Cu in traditional aqueous electrolyte suffers from the broad product distribution and low faradaic efficiency ¹. Moreover, in aqueous electrolytes, higher overpotentials are required to convert CO₂ into the intermediates on metal electrodes¹. To overcome these limitations, ionic liquids (ILs) have been proposed as supporting electrolytes due to some unique properties such as the ability to interact with CO₂². ILs have been reported to affect the product selectivity and kinetics in CO₂ electroreduction on different metals such as silver ^{2, 3}.

In this study, we have investigated the impact of using ionic liquids in CO₂ electroreduction on Cu catalysts. CO₂ electroreduction experiments were done on Cu flags for 30 mins at different potentials and in a H-type electrochemical cell. The results showed that ionic liquids affect the product selectivity even at very low concentrations. It was observed that by adding just 10 mM 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][NTF₂]) to the 0.1 M KHCO₃ electrolyte, the total current density increased by 63% at -1.1 V (vs RHE). Moreover, a 80% increase in FE at -1.1 V (vs RHE) for methane was observed in the ionic liquid/water mixture. We also detected a 50% increase in faradaic efficiency for formate at the lowest examined potential (-0.91 V) when adding the ionic liquid.

1. Hori, Y., Electrochemical CO₂ reduction on metal electrodes. In Modern Aspects of Electrochemistry, Vayenas, C. G.; White, R. E.; Gamboa-Aldeco, M. E., Eds. Springer: New York, 2008; Vol. 42, pp 89-189.

2. Mu, T.; Chen, Y., Conversion of CO₂ to value-added products mediated by ionic liquids. Green Chemistry 2019.

3. Rosen, B. A.; Salehi-Khojin, A.; Thorson, M. R.; Zhu, W.; Whipple, D. T.; Kenis, P. J. A.; Masel, R. I., Ionic liquid-mediated selective conversion of CO₂ to CO at low overpotentials. Science 2011,334(6056), 643-644.