Ruthenium-Substituted\nPolyoxoanion Serves as Redox\nShuttle and Intermediate Stabilizer in Selective Electrooxidation\nof Ethylene to Ethylene Glycol

The\nhigh carbon intensity of present-day ethylene glycol (EG) production\nmotivates interest in electrifying ethylene oxidation. Noting poor\nkinetics in prior reports of the organic electrooxidation of small\nhydrocarbons, we explored the design of mediators that activate and\nsimultaneously stabilize light alkenes. A ruthenium-substituted polyoxometalate\n(Ru-POM, {Si[Ru(H<sub>2</sub>O)W<sub>11</sub>O<sub>39</sub>]}<sup>5–</sup>) achieves 82% faradaic efficiency in EG production\nat 100 mA/cm<sup>2</sup> under ambient conditions. Via the union of <i>in situ</i> spectroscopic techniques, electrochemical studies,\nand density functional theory calculations, we find evidence of a\ntwo-step oxidation mechanism: Ru-POM first undergoes electrochemical\noxidation to the high valent state, activating ethylene via partial\noxidation and forming an intermediate complex; this intermediate complex\nthen migrates to the anode where it undergoes further oxidation to\nproduce EG. The Ru-POM-mediated electrocatalytic system reduces the\nprojected energy consumption required in EG production, requiring\n9 GJ per ton of EG (and accompanied by 0.04 ton H<sub>2</sub> coproduction),\ncompared to 20–30 GJ/ton in typical prior processes.