室温离子液体中的二氧化碳还原：电极材料，阳离子和阴离子的选择的影响,The Journal of Physical Chemistry C

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室温离子液体中的二氧化碳还原：电极材料，阳离子和阴离子的选择的影响
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2016-11-11 00:00:00 , DOI: 10.1021/acs.jpcc.6b10564
Eden E. L. Tanner ₁ , Christopher Batchelor-McAuley ₁ , Richard G. Compton ₁

Affiliation

在室温离子液体（RTIL）中系统地研究了二氧化碳的电还原，以建立电极材料，阳离子和阴离子对还原机理的影响。使用循环伏安法在1-丁基-3-甲基咪唑鎓双（三氟甲基磺酰基）酰亚胺（[Bmim] [NTf ₂]）。在银电极上，观察到扩散限制的还原峰值电流，而对于金，峰值电流密度小6倍。铂或玻璃碳都没有明显的减少。此外，在银上，还原所需的过电势降低了约50％。与金相比为1.5V。接下来，通过使用以下RTIL，在银电极上显示出阳离子效应和阴离子效应：1-丁基-1-甲基吡咯烷二（三氟甲基磺酰基）-酰亚胺（[Bmpyrr] [NTf ₂ ]），1-乙基-3-甲基咪唑鎓双（三氟甲基磺酰基）酰亚胺（[Emim] [NTf ₂ ]），1-丙基-3-甲基-咪唑鎓双（三氟甲基磺酰基）酰亚胺（[Pmim]-[NTf ₂]），1-丁基-3-甲基-咪唑鎓三（五氟乙基）三氟磷酸酯（[Bmim] [FAP]）和1-丁基-3-甲基咪唑鎓四氟硼酸酯（[Bmim] [BF ₄ ]）。阴离子和阳离子效应的研究可通过使用基于IL的Ag / Ag ⁺参比电极来实现，每个参比电极中的溶剂均由主要溶液中使用的RTIL组成。为了直接比较不同溶剂之间的CO ₂还原电势，以钴ce /钴茂金属对为标准，从而报告了校正后的相对电势。在[Bmim] [NTf ₂ ]中，相对于钴ce /并茂，在[Bmimrr] [NTf ₂ ]中，在-1.20 V时，以及在[Emim] [NTf ₂ ]中，观察到银上的峰值电流]和[Pmim] [NTf ₂ ]处于-1.50V 。在阴离子中，[Bmim] [BF ₄ ]中观察到的峰值电流发生在与[Bmim] [NTf ₂ ]相当的电位下（-1.10 V vs钴ce /钴茂金属），而[Bmim] [FAP]中的CO ₂还原在-1.60 V处观察到。这项工作提供了实验证据，表明银有助于二氧化碳的内球还原，并提出了可能的机理。

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Carbon Dioxide Reduction in Room-Temperature Ionic Liquids: The Effect of the Choice of Electrode Material, Cation, and Anion

The electroreduction of carbon dioxide is systematically investigated in room-temperature ionic liquids (RTILs) to establish the effect of the electrode material, the cation, and the anion on the mechanism of reduction. Silver, gold, platinum, and glassy carbon macroelectrodes are investigated using cyclic voltammetry in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Bmim][NTf₂]). On silver electrodes, a diffusion-limited reductive peak current is observed, while for gold, the peak current density is 6 times smaller. No appreciable reduction is observable on either platinum or glassy carbon. Moreover, on silver, the overpotential required for reduction is reduced by ca. 1.5 V compared with gold. Next, a cation effect and an anion effect are demonstrated on a silver electrode, with the use of the following RTILs: 1-butyl-1-methylpyrrolodinium bis(trifluoromethylsulfonyl)-imide ([Bmpyrr][NTf₂]), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Emim][NTf₂]), 1-propyl-3-me-thylimidazolium bis(trifluoromethylsulfonyl)imide ([Pmim]-[NTf₂]), 1-butyl-3-met-hylimidazolium tris(pentafluoroethyl)trifluorophosphate ([Bmim][FAP]), and 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF₄]). The study of the anion and cation effect is enabled by the use of IL-based Ag/Ag⁺ reference electrodes, with the solvent in each reference electrode composed of the RTIL used in the primary solution. To allow direct comparison of CO₂ reduction potentials between different solvents, the cobaltocenium/cobaltocene couple is used as a standard, allowing corrected relative potentials to be reported. The peak current on silver was observed in [Bmim][NTf₂] at −1.1 V vs cobaltocenium/cobaltocene, in [Bmpyrr][NTf₂] at −1.20 V, and in [Emim][NTf₂] and [Pmim][NTf₂] at −1.50 V. Of the anions, the peak current observed in [Bmim][BF₄] occurs at a comparable potential to [Bmim][NTf₂] (−1.10 V vs cobaltocenium/cobaltocene), while the reduction of CO₂ in [Bmim][FAP] was observed at −1.60 V. This work provides experimental evidence that silver facilitates the inner-sphere reduction of carbon dioxide, and a possible mechanism is proposed.

更新日期：2016-11-11

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