Effect of anion in diluted imidazolium-based ionic liquid/buffer electrolytes for CO2 electroreduction on copper
By Golru, Samaneh Sharifi; Biddinger, Elizabeth J.
Published in Electrochimica Acta
Electrochimica Acta
2020
Abstract
A series of ILs containing the same cation (1?butyl?3-methylimidazolium ([BMIM]+)) but different anions (bis(trifluoromethylsulfonyl)imide ([NTF2]?), triflate ([OTF]?), acetate ([Ac]?), chloride ([Cl]?), and dicyanamide ([DCA]?)) were used to study the effect of anion in diluted imidazolium-based ionic liquid/buffer electrolytes on product selectivity and activity of copper electrodes in CO2 electroreduction. The onset potential shifted to more positive potentials by adding ILs to the CO2-saturated electrolytes. Faradaic efficiency (FE%) of formate for all ILs (except for [BMIM][DCA]) increased compared to the electrolyte without any IL at all potentials. The maximum FEformate (38.7%) was observed for [BMIM][NTF2] at -0.92 V. [BMIM][DCA] had the highest FE% for hydrogen and the lowest FE% for hydrocarbons. By using X-ray photoelectron spectroscopy, the maximum amount of IL adsorbed on the surface was obtained for [BMIM][DCA] which had the highest hydrophilicity and lowest CO2 affinity. These results underscore the importance of anions when using ILs for CO2 electroreduction.