Electrochemical reduction of CO₂ has been proposed as a promising way to attenuate the CO₂ level in the atmosphere and consequently, mitigate the global warming. Furthermore, several valuable chemicals and fuels can be produced by CO₂ electroreduction. Although copper catalysts are of interest due to their ability to produce hydrocarbons and alcohols, they produce a wide verity of products and need high overpotentialsin traditional aqueous electrolytes¹. One of the methods to address these obstacles is to use ionic liquids (ILs) in the electrolyte. ILs are cation-anion couples which have unique properties such as high CO₂ solubility. In CO₂ electroreduction, ILs can play different roles such as co-catalyst, electrolyte, or CO₂ absorbent. It has been reported that product selectivity and the reaction rate in CO₂ electrocution is significantly impacted when using ionic liquids^{2, 3}.

Here, the effect of using ionic liquids in CO₂ electroreduction on product selectivity and activity of Cu catalysts has been studied. For this purpose, Cu foils were first electropolished in 1M phosphoric acid for 300 sec. CO₂ electroreduction was then performed on Cu catalysts for 30 mins at different potentials. According to the results, ionic liquids affected the product selectivity even in a diluted IL/water mixture. The results showed that adding 10 mM 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][NTF₂]) to the 0.1 M KHCO₃ electrolyte leads to a 63% increase in the total current density at -1.1 V (vs RHE). A 50% increase in formate faradaic efficiency at -0.91 V was also detected when adding the IL to the electrolyte. Moreover, the faradaic efficiency of methane increased by 80% at -1.1 V (vs RHE) in the ionic liquid/water mixture. The results demonstrate how ILs influence the CO₂ reduction on Cu catalysts.

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. Zhou, F.; Liu, S.; Yang, B.; Wang, P.; Alshammari, A. S.; Deng, Y., Highly selective and stable electro-catalytic system with ionic liquids for the reduction of carbon dioxide to carbon monoxide. Electrochemistry Communications 2015,55(0), 43-46.