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The inhibition of the proton donor ability of bicarbonate promotes the electrochemical conversion of CO2 in bicarbonate solutions
Journal of CO2 Utilization ( IF 7.7 ) Pub Date : 2021-04-16 , DOI: 10.1016/j.jcou.2021.101521
Oriol Gutiérrez-Sánchez , Nick Daems , Willem Offermans , Yuvraj Y. Birdja , Metin Bulut , Deepak Pant , Tom Breugelmans

Gaseous CO2 solutions are widely used for CO2 electrochemical conversion to various valuable products. However, capture, liberation and storage of gaseous CO2 prior to reduction is cumbersome and costly. CO2 electrocatalytic reduction from captured CO2 (in the form of concentrated bicarbonate solution) offers an option to optimize CO2 reduction processes. Using concentrated bicarbonate solutions from captured CO2 as large carbon feedstock and reducing CO2 directly from bicarbonate electrolyte remain a challenge. Indeed, current efficiency is too low (i.e. low selectivity and/or activity) as a consequence of the strong competition with the hydrogen evolution reaction, which bicarbonate promotes to a great extent. In this study, up to 2 M bicarbonate solution is used as electrolyte (mimicking a captured CO2 solution from an alkaline media) for a CO2 electrochemical reduction system, which potentially pretends to be a 2 M carbon source, compared to 0.033 M present in a saturated gaseous CO2 solution. In order to improve the Faradaic efficiency of the process and thereby making the CO2 electrocatalytic reduction from a bicarbonate feedstock an efficient system and attractive alternative for the reduction starting from gaseous CO2, a reaction mechanism where bicarbonate acts as a CO2 donor instead of as a proton donor is proposed. To achieve such property, we inhibit the proton donor ability of bicarbonate and water by covering the surface of the electrode with cationic surfactants, allowing non-polar molecules, like the CO2 derived from the equilibrium with bicarbonate, to diffuse to the surface of the electrode while avoiding bicarbonate and water to promote the hydrogen evolution reaction. To the best of our knowledge, the Faradaic Efficiency to formate obtained in this study (>70 %) sets a new benchmark in systems involving unsaturated and saturated bicarbonate solutions without previously purging CO2.



中文翻译:

碳酸氢盐质子给体能力的抑制促进了碳酸氢盐溶液中CO 2的电化学转化

气态CO 2溶液被广泛用于将CO 2电化学转化为各种有价值的产品。然而,在还原之前捕获,释放和储存气态CO 2既麻烦又昂贵。从捕获的CO 2(以浓碳酸氢盐溶液的形式)中进行的CO 2电催化还原提供了优化CO 2还原过程的选择。使用捕获的CO 2中的浓缩碳酸氢盐溶液作为大型碳原料并减少CO 2直接来自碳酸氢盐电解质仍然是一个挑战。实际上,由于与氢释放反应的激烈竞争,电流效率太低(即低的选择性和/或活性),而氢释放反应在很大程度上促进了氢的释放。在这项研究中,最多使用2 M的碳酸氢盐溶液作为电解质(模仿从碱性介质中捕获的CO 2溶液)用于CO 2电化学还原系统,与现有的0.033 M相比,它可能假装为2 M碳源。在饱和的气态CO 2溶液中。为了提高该方法的法拉第效率,从而制得CO 2从碳酸氢盐原料进行电催化还原是一种有效的系统,并且是从气态CO 2开始还原的有吸引力的替代方法,提出了一种反应机理,其中碳酸氢盐充当CO 2供体而不是质子供体。为了实现这种特性,我们通过用阳离子表面活性剂覆盖电极表面,允许非极性分子(如CO 2)来抑制碳酸氢盐和水的质子供体能力。从碳酸氢盐的平衡中衍生出来,扩散到电极的表面,同时避免碳酸氢盐和水促进氢的释放反应。据我们所知,在这项研究中获得的法拉第甲酸生成效率(> 70%)为涉及不饱和和饱和碳酸氢盐溶液而无需事先清除CO 2的系统树立了新的标杆。

更新日期:2021-04-16
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