Data Sheet 1_Efficient electrocatalytic reduction of CO2 on an Ag catalyst in 1-ethyl-3-methylimidazolium ethylsulfate, with its co-catalytic role as a supporting electrolyte during the reduction in an acetonitrile medium.docx

CO2 electrochemical reduction reactions (CO2ERR) has shown great promise in reducing greenhouse gas emissions while also producing useful chemicals. In this contribution, we describe the CO2ERR at different catalysts using 1-ethyl-3-methylimidazolium ethyl sulfate [emim][EtSO4] ionic liquid (IL) as a solvent and as a supporting electrolyte. CO2ERR occurs at Ag and Cu catalysts at a lower overpotential than that at Au, Pt, and boron-doped diamond (BDD) catalysts. In addition, we report that ILs play a better co-catalytic role when used as a supporting electrolyte during CO2ERR in an acetonitrile (AcN) medium than the conventional supporting electrolyte, tetrabutylammonium hexafluorophosphate [TBA][PF6] in AcN. Furthermore, it is found that imidazolium-based cations ([emim]+) play a significant co-catalytic role during the reduction compared to [TBA]+ and pyrrolidinium [empyrr]+ cations, while anions of the ILs play no such role. The formation of CO from the CO2ERR was detected using cyclic voltammetry at an Ag catalyst both in [emim][EtSO4] as well as in an AcN solvent containing [emim][EtSO4] as a supporting electrolyte. The product of the CO2 reduction in this IL medium at the Ag catalyst is CO, which can be converted to synthetic liquid fuels by coupling the process with the Fischer–Tropsch process or through the conversion of CO2 into fuels based on green hydrogen by the Sabatier process, that is, methanation of CO2 on industrial scale, in the future.

二氧化碳电化学还原反应（CO₂ electrochemical reduction reactions，缩写CO₂ERR）在削减温室气体排放的同时还可制备高附加值化学品，展现出极佳的应用前景。本研究中，我们针对不同催化剂体系下的二氧化碳电化学还原反应展开了系统表征与描述，实验采用硫酸乙酯1-乙基-3-甲基咪唑鎓([emim][EtSO₄])离子液体（ionic liquid，IL）作为溶剂与支持电解质。相较于金（Au）、铂（Pt）以及掺硼金刚石（boron-doped diamond，BDD）催化剂，银（Ag）与铜（Cu）催化剂上的二氧化碳电化学还原反应所需过电位更低。此外，我们发现，在乙腈（acetonitrile，AcN）介质中进行二氧化碳电化学还原反应时，以离子液体作为支持电解质的体系，其共催化性能优于以传统支持电解质六氟磷酸四丁基铵([TBA][PF₆])溶解于乙腈所构建的体系。进一步研究表明，相较于[TBA]+与吡咯烷鎓([empyrr]+)阳离子，咪唑鎓类阳离子([emim]+)在还原过程中发挥了更为显著的共催化作用，而离子液体的阴离子则无此类功效。在以[emim][EtSO₄]为溶剂，以及以含[emim][EtSO₄]的乙腈溶液作为支持电解质的两种体系中，我们均可通过循环伏安法（cyclic voltammetry）检测到银催化剂上二氧化碳电化学还原反应生成一氧化碳（CO）的过程。在该离子液体介质中，银催化剂上的二氧化碳还原产物为一氧化碳，未来可通过将该过程与费托合成（Fischer–Tropsch）工艺耦合，或是借助基于绿氢的萨巴捷（Sabatier）工艺（即规模化二氧化碳甲烷化技术）将一氧化碳转化为合成液态燃料。