Jovanovic Sven, Jakes Peter, Merz Steffen, Daniel Davis Thomas, Eichel Rüdiger-A, Granwehr Josef
Institute of Energy and Climate Research - Fundamental Electrochemistry (IEK-9), Forschungszentrum Jülich GmbH, Willhelm-Johnen-Straße, Jülich, Germany.
Institute of Physical Chemistry (IPC), RWTH Aachen University, Aachen, Germany.
Commun Chem. 2023 Dec 6;6(1):268. doi: 10.1038/s42004-023-01065-3.
The electrolytic reduction of CO in aqueous media promises a pathway for the utilization of the green house gas by converting it to base chemicals or building blocks thereof. However, the technology is currently not economically feasible, where one reason lies in insufficient reaction rates and selectivities. Current research of CO electrolysis is becoming aware of the importance of the local environment and reactions at the electrodes and their proximity, which can be only assessed under true catalytic conditions, i.e. by in operando techniques. In this work, multinuclear in operando NMR techniques were applied in order to investigate the evolution of the electrolyte chemistry during CO electrolysis. The CO electroreduction was performed in aqueous NaHCO or KHCO electrolytes at silver electrodes. Based on C and Na NMR studies at different magnetic fields, it was found that the dynamic equilibrium of the electrolyte salt in solution, existing as ion pairs and free ions, decelerates with increasingly negative potential. In turn, this equilibrium affects the resupply rate of CO to the electrolysis reaction from the electrolyte. Substantiated by relaxation measurements, a mechanism was proposed where stable ion pairs in solution catalyze the bicarbonate dehydration reaction, which may provide a new pathway for improving educt resupply during CO electrolysis.
在水介质中对CO进行电解还原，有望通过将温室气体转化为基础化学品或其结构单元，提供一条利用该气体的途径。然而，目前这项技术在经济上并不可行，其中一个原因是反应速率和选择性不足。当前对CO电解的研究逐渐意识到局部环境以及电极及其附近反应的重要性，而这只能在真正的催化条件下，即通过原位技术来评估。在这项工作中，应用了多核原位NMR技术，以研究CO电解过程中电解质化学的演变。CO的电还原在银电极上的NaHCO或KHCO水性电解质中进行。基于在不同磁场下的C和Na NMR研究，发现溶液中电解质盐以离子对和自由离子形式存在的动态平衡随着电势变得越来越负而减速。反过来，这种平衡会影响CO从电解质到电解反应的再供应速率。通过弛豫测量得到证实，提出了一种机制，即溶液中稳定的离子对催化碳酸氢盐脱水反应，这可能为改善CO电解过程中的反应物再供应提供一条新途径。
