Noh Seonmyeong, Cho Yoon Jin, Zhang Gong, Schreier Marcel
Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States.
Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States.
J Am Chem Soc. 2023 Dec 20;145(50):27657-27663. doi: 10.1021/jacs.3c09687. Epub 2023 Nov 29.
The electroreduction of CO plays an important role in achieving a net-zero carbon economy. Imidazolium cations can be used to enhance the rate of CO reduction reactions, but the origin of this promotion remains poorly understood. In this work, we show that in the presence of 1-ethyl-3-methylimidazolium (EMIM), CO reduction on Ag electrodes occurs with an apparent activation energy near zero, while the applied potential influences the rate through the pre-exponential factor. Our findings suggest that the CO reduction rate is controlled by the initial state entropy, which depends on the applied potential through the organization of cations at the electrochemical interface. Further characterization shows that the C2-proton of EMIM is consumed during the reaction, leading to the collapse of the cation organization and a decrease in the catalytic performance. Our results have important implications for understanding the effect of potential on reaction rates, as they indicate that the common picture based on vibrational activation of electron transfer reactions is insufficient for describing the impact of potential in complex systems, such as CO reduction in the presence of imidazolium cations.
CO的电还原在实现净零碳经济中起着重要作用。咪唑阳离子可用于提高CO还原反应的速率，但这种促进作用的起源仍知之甚少。在这项工作中，我们表明，在1-乙基-3-甲基咪唑鎓（EMIM）存在下，Ag电极上的CO还原反应的表观活化能接近零，而外加电势通过指前因子影响反应速率。我们的研究结果表明，CO还原速率由初始态熵控制，初始态熵通过电化学界面处阳离子的排列依赖于外加电势。进一步的表征表明，EMIM的C2-质子在反应过程中被消耗，导致阳离子排列的崩溃和催化性能的下降。我们的结果对于理解电势对反应速率的影响具有重要意义，因为它们表明基于电子转移反应振动活化的常见图景不足以描述电势在复杂系统中的影响，例如在咪唑阳离子存在下的CO还原。
