Dattila Federico, Fortunati Alessia, Zammillo Federica, Guzmán Hilmar, López Núria, Hernández Simelys
CREST Group, Department of Applied Science and Technology (DISAT), Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Turin, Italy.
Institute of Chemical Research of Catalonia (ICIQ-CERCA), The Barcelona Institute of Science and Technology (BIST), Avinguda dels Països Catalans 16, 43007 Tarragona, Spain.
ACS Catal. 2024 Oct 17;14(21):16166-16174. doi: 10.1021/acscatal.4c05012. eCollection 2024 Nov 1.
Electrochemical CO reduction (COR) allows us to close the carbon cycle and store intermittent renewable energy into chemical products. Among these, syngas, a mixture of hydrogen and carbon monoxide, is particularly valuable due to its high market share and the low energy required for its electrocatalytic production. In addition to catalyst optimization, lately, electrolyte modifications to achieve a suitable CO/H ratio have also been considered. Ionic liquid (IL)-based electrolytes have enabled high faradaic efficiency toward CO, depending on the chemical properties of the IL. In this work, we rationalized through density functional theory (DFT) descriptors the competition between hydrogen evolution (HER) and COR on silver in imidazolium-based electrolytes, developing a DFT-based analytical model. The electrolyte anion regulates the concentration ratio between cationic and carbene species of ILs cation, respectively, between the 1-ethyl-3-methylimidazolium cation (EMIM) and carbene (EMIM:) species and between the 1-butyl-3-methylimidazolium cation (BMIM) and carbene (BMIM:). The latter species, if formed, hinders the COR by blocking the active sites or trapping CO in solution. In the case of weak Lewis base anions as fluorinated ones, EMIM (BMIM) cations, which serve as cocatalysts in COR, are more abundant, allowing high CO partial current densities and high electrochemically active surface area. Applying the here-defined descriptors to ILs not yet tested makes it possible to predict the HER and COR selectivity on silver, thus enabling guidelines for designing better ILs for COR.
电化学CO还原（COR）使我们能够闭合碳循环，并将间歇性可再生能源存储到化学产品中。其中，合成气，即氢气和一氧化碳的混合物，因其高市场份额和电催化生产所需的低能量而特别有价值。除了优化催化剂外，最近还考虑了通过电解质改性来实现合适的CO/H比。基于离子液体（IL）的电解质能够实现对CO的高法拉第效率，这取决于IL的化学性质。在这项工作中，我们通过密度泛函理论（DFT）描述符合理化了基于咪唑鎓盐的电解质中银上析氢反应（HER）和COR之间的竞争，开发了一个基于DFT的分析模型。电解质阴离子分别调节IL阳离子的阳离子和卡宾物种之间的浓度比，即1-乙基-3-甲基咪唑鎓阳离子（EMIM）与卡宾（EMIM:）物种之间以及1-丁基-3-甲基咪唑鎓阳离子（BMIM）与卡宾（BMIM:）之间的浓度比。后一种物种如果形成，会通过阻塞活性位点或在溶液中捕获CO来阻碍COR。在弱路易斯碱阴离子如氟化阴离子的情况下，作为COR助催化剂的EMIM（BMIM）阳离子更为丰富，从而允许高CO分电流密度和高电化学活性表面积。将这里定义的描述符应用于尚未测试的IL，可以预测银上的HER和COR选择性，从而为设计更好的用于COR的IL提供指导。
