Gordon and Mary Cain Department of Chemical Engineering, Louisiana State University , Baton Rouge, Louisiana 70803, United States.
J Am Chem Soc. 2017 Mar 8;139(9):3399-3405. doi: 10.1021/jacs.6b11023. Epub 2017 Feb 22.
Electrochemical reduction of CO provides an opportunity to store renewable energy as fuels with much greater energy densities than batteries. Product selectivity of the reduction reaction is known to be a function of the electrolyte and electrode; however, electrodes modified with functional ligands may offer new methods to control selectivity. Here, we report the electrochemical reduction of CO at functionalized Au surfaces with three thiol-tethered ligands: 2-mercaptopropionic acid, 4-pyridinylethanemercaptan, and cysteamine. Remarkably, Au electrodes modified with 4-pyridinylethanemercaptan show a 2-fold increase in Faradaic efficiency and 3-fold increase in formate production relative to Au foil. Conversely, electrodes with 2-mercaptopropionic acid ligands show nearly 100% Faradaic efficiency toward the hydrogen evolution reaction, while cystemine-modified electrodes show 2-fold increases in both CO and H production. We propose a proton-induced desorption mechanism associated with pK of the functionalized ligand as responsible for the dramatic selectivity changes.
电化学还原 CO 提供了一个机会，可以将可再生能源储存为燃料，其能量密度比电池高得多。还原反应的产物选择性已知是电解质和电极的函数；然而，用功能配体修饰的电极可能提供控制选择性的新方法。在这里，我们报告了在三种巯基键合配体（2-巯基丙酸、4-吡啶乙硫醇和半胱胺）修饰的 Au 表面上 CO 的电化学还原。值得注意的是，与 Au 箔相比，用 4-吡啶乙硫醇修饰的 Au 电极的法拉第效率提高了 2 倍，甲酸的生成量提高了 3 倍。相反，带有 2-巯基丙酸配体的电极对析氢反应的法拉第效率几乎达到 100%，而半胱胺修饰的电极使 CO 和 H 的生成量增加了 2 倍。我们提出了一种与功能化配体的 pK 相关的质子诱导脱附机制，该机制负责显著的选择性变化。
