(41b) Enhanced CO2 Electroreduction in Selectivity Tuned By Anion Modification of the Ionic Liquids

Authors: 
Feng, J., University of Chinese Academy of Science
Zeng, S., Chinese Academy of Sciences
Zhang, S., Beijing Key Laboratory of Ionic Liquids Clean Process,CAS Key Labroratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences
Zhang, X., Beijing Key Laboratory of Ionic Liquids Clean Process,CAS Key Labroratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences
Enhanced CO2 electroreduction in selectivity tuned by anion modification of the ionic liquids

Jianpeng Feng a,b, Shaojuan Zenga, Suojiang Zhang a , Xiangping Zhang a,*

a Institute of Process Engineering, Chinese Academy of Sciences, 100190, Beijing, China

bUniversity of Chinese Academy of Science, Beijing 100049, China

*Corresponding author: xpzhang@ipe.ac.cn

In the past hundreds years, the unrestrained combustion of non-renewable fossil fuels leads to an aggravated energy crisis and a continuously rising level of atmospheric carbon dioxide (CO2). which has created serious environmental, social and global ecological issues1, 2. However, CO2 is also a cheap, abundant and renewable C1-feedstock that can be converted into useful chemicals. Electrochemical reduction was extensively studied owing to their mild reaction conditions and easy implementation for practical applications. Moreover, they can directly use the seasonal, geographical, and intermittent energy (tied, wind, and solar et al.). However, the low solubility of CO2 and complicated reaction process in aqueous solution render CO2 reduction inefficient. Ionic liquid (IL) has been proven to be a promising reaction medium for CO2 electrochemical reaction because of its unique physicochemical properties (e.g., high CO2 solubility, high intrinsic ionic conductivity, wide electrochemical potential windows )3, 4

In this work, Herein, we present an efficient CO2 electroreduction system based on a diverse class of imidazolium ILs, including a novel superbase IL 1-Butyl-3-Methylimidazolium 1,2,4-Triazolide ([Bmim][124Triz]). The superbase IL has a superior capacity of 0.726 mol CO2 per mol IL, and the high concentration of dissolved CO2 in the electrolyte is favorable for the fast transport of CO2 to the cathode surface. On Pb electrode, the applied potential for CO2 reduction to formic acid (HCOOH) was lowered from circa -1.97 V to -1.78 V (vs. Ag/Ag+) compared to [Bmim][PF6] IL. For now it was widely reported that the reduced form from imidazolium cation, namely, imidazolium neutral radical serves as the reaction site for CO2 reduction, nevertheless, we found that in the HCOOH formation on Pb electrode, the chemical binding of the [124Triz]- anion and CO2 molecule can decrease the activation energy, significantly. Furthermore, within the same strategy, the highest Faradaic efficiency (98.4%) at partial current density of 11.7 mA cm-2 for CO was obtained on Ag in ILs system to date. Our finding about the role of the anion on CO2 electroreduction will stimulate to develop more novel anions to enhance this reaction process and open a potential way for the efficient utilization of CO2.

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