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 liquids2, 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. 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.Mu, T.; Chen, Y., Conversion of CO2 to value-added products mediated by ionic liquids. Green Chemistry 2019.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.