Overpotentials and Faraday Efficiencies in CO2 Electrocatalysis-the Impact of 1-Ethyl-3-Methylimidazolium Trifluoromethanesulfonate

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• 作者：Sebastian S. Neubauer ; Ralf K. Krause ; Bernhard Schmid ; Dirk M. Guldi and Gü ; nter Schmid
• 刊名：Advanced Energy Materials
• 出版年：2016
• 出版时间：May 11, 2016
• 年：2016
• 卷：6
• 期：9
• 全文大小：605K
• ISSN：1614-6840

文摘

The mixtures of room temperature ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIM]TFO) and water as electrolytes for reduction of CO₂ to CO are reported. Linear sweep voltammetry shows overpotentials for CO₂ reduction and the competing hydrogen evolution reaction (HER), both of which vary as a function of [EMIM]TFO concentration in the range from 4 × 10^−3mallCaps">m (0.006 mol%) to 4869 × 10^−3mallCaps">m (50 mol%). A steady lowering of overpotentials up to an optimum for 334 × 10−³mallCaps">m is identified. At 20 mol% and more of [EMIM]TFO, a significant CO₂ reduction plateau and inhibition of HER, which is limited by H₂O diffusion, is noted. Such a plateau in CO₂ reduction correlates to high CO Faraday efficiencies. In case of 50 mol% [EMIM]TFO, a broad plateau spanning over a potential range of 0.58 V evolves. At the same time, the overpotential for HER is increased by 1.20 V when compared to 334 × 10^−3mallCaps">m and, in turn, HER is largely inhibited. The Faraday efficiencies for CO and H₂ formation feature 95.6% ± 6.8% and 0.5% ± 0.3%, respectively, over a period of 3 h in a separator divided cell. Cathodic as well as anodic electrochemical stability of the electrolyte throughout this time period is corroborated in ¹H NMR spectroscopic measurements.