Bui Anna T, Hartley Niamh A, Thom Alex J W, Forse Alexander C
Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
J Phys Chem C Nanomater Interfaces. 2022 Aug 25;126(33):14163-14172. doi: 10.1021/acs.jpcc.2c03752. Epub 2022 Aug 12.
Electrochemical carbon dioxide capture recently emerged as a promising alternative approach to conventional energy-intensive carbon-capture methods. A common electrochemical capture approach is to employ redox-active molecules such as quinones. Upon electrochemical reduction, quinones become activated for the capture of CO through a chemical reaction. A key disadvantage of this method is the possibility of side-reactions with oxygen, which is present in almost all gas mixtures of interest for carbon capture. This issue can potentially be mitigated by fine-tuning redox potentials through the introduction of electron-withdrawing groups on the quinone ring. In this article, we investigate the thermodynamics of the electron transfer and chemical steps of CO capture in different quinone derivatives with a range of substituents. By combining density functional theory calculations and cyclic voltammetry experiments, we support a previously described trade-off between the redox potential and the strength of CO capture. We show that redox potentials can readily be tuned to more positive values to impart stability to oxygen, but significant decreases in CO binding free energies are observed as a consequence. Our calculations support this effect for a large series of anthraquinones and benzoquinones. Different trade-off relationships were observed for the two classes of molecules. These trade-offs must be taken into consideration in the design of improved redox-active molecules for electrochemical CO capture.
电化学二氧化碳捕集最近成为一种有前景的替代传统高能耗碳捕集方法的途径。一种常见的电化学捕集方法是使用醌等氧化还原活性分子。在电化学还原时，醌通过化学反应被激活以捕获二氧化碳。该方法的一个关键缺点是与氧气发生副反应的可能性，而氧气几乎存在于所有对碳捕集感兴趣的气体混合物中。通过在醌环上引入吸电子基团来微调氧化还原电位，这个问题可能会得到缓解。在本文中，我们研究了一系列具有不同取代基的醌衍生物中二氧化碳捕集的电子转移和化学步骤的热力学。通过结合密度泛函理论计算和循环伏安实验，我们支持了先前描述的氧化还原电位与二氧化碳捕集强度之间的权衡。我们表明，氧化还原电位可以很容易地调整到更正的值以赋予对氧气的稳定性，但结果是观察到二氧化碳结合自由能显著降低。我们的计算支持了一大系列蒽醌和苯醌的这种效应。对于这两类分子观察到了不同的权衡关系。在设计用于电化学二氧化碳捕集的改进氧化还原活性分子时，必须考虑这些权衡。
