Lum Yanwei, Cheng Tao, Goddard William A, Ager Joel W
Joint Center for Artificial Photosynthesis and Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States.
Department of Materials Science and Engineering , University of California , Berkeley , California 94720 , United States.
J Am Chem Soc. 2018 Aug 1;140(30):9337-9340. doi: 10.1021/jacs.8b03986. Epub 2018 Jul 20.
Numerous studies have examined the electrochemical reduction of CO (COR) to oxygenates (e.g., ethanol). None have considered the possibility that oxygen in the product might arise from water rather than from CO. To test this assumption, CO reduction was performed in HO electrolyte. Surprisingly, we found that 60-70% of the ethanol contained O, which must have originated from the solvent. We extended our previous all-solvent density functional theory metadynamics calculations to consider the possibility of incorporating water, and indeed, we found a new mechanism involving a Grotthuss chain of six water molecules in a concerted reaction with the *C-CH intermediate to form *CH-CH(OH), subsequently leading to (O)ethanol. This competes with the formation of ethylene that also arises from *C-CH. These unforeseen results suggest that all previous studies of COR under aqueous conditions must be reexamined.
众多研究已考察了将一氧化碳（CO）电化学还原为含氧化合物（如乙醇）的过程。但尚无研究考虑过产物中的氧可能来源于水而非CO的可能性。为验证这一假设，在重水（D₂O）电解质中进行了CO还原反应。令人惊讶的是，我们发现60 - 70%的乙醇含有氧，这些氧必定源自溶剂。我们扩展了之前的全溶剂密度泛函理论元动力学计算，以考虑引入水的可能性，实际上，我们发现了一种新机制，即六个水分子形成的Grotthuss链与C-CH中间体协同反应，形成CH-CH(OH)，随后生成（含O）乙醇。这与同样由*C-CH生成乙烯的过程相互竞争。这些意外结果表明，之前所有在水性条件下进行的CO还原研究都必须重新审视。
