Ruthenium-Substituted Polyoxoanion Serves as Redox Shuttle and Intermediate Stabilizer in Selective Electrooxidation of Ethylene to Ethylene Glycol

Creators: Yu, Jiaqi¹; Musgrave, Charles Bruce^{1, 2}; Chen, Qiucheng¹; Yang, Yi¹; Tian, Cong¹; Hu, Xiaobing¹; Su, Guangcan¹; Shin, Heejong¹; Ni, Weiyan¹; Chen, Xinqi¹; Ou, Pengfei¹; Liu, Yuan¹; Schweitzer, Neil M.¹; Meira, Debora Motta^{3, 4}; Dravid, Vinayak P.¹; Goddard, William A.²; Xie, Ke¹; Sargent, Edward H.¹

1. Northwestern University
2. California Institute of Technology
3. Argonne National Laboratory
4. Canadian Light Source (Canada)

Abstract

The high carbon intensity of present-day ethylene glycol (EG) production motivates interest in electrifying ethylene oxidation. Noting poor kinetics in prior reports of the organic electrooxidation of small hydrocarbons, we explored the design of mediators that activate and simultaneously stabilize light alkenes. A ruthenium-substituted polyoxometalate (Ru-POM, {Si[Ru(H₂O)W₁₁O₃₉]}^5–) achieves 82% faradaic efficiency in EG production at 100 mA/cm² under ambient conditions. Via the union of in situ spectroscopic techniques, electrochemical studies, and density functional theory calculations, we find evidence of a two-step oxidation mechanism: Ru-POM first undergoes electrochemical oxidation to the high valent state, activating ethylene via partial oxidation and forming an intermediate complex; this intermediate complex then migrates to the anode where it undergoes further oxidation to produce EG. The Ru-POM-mediated electrocatalytic system reduces the projected energy consumption required in EG production, requiring 9 GJ per ton of EG (and accompanied by 0.04 ton H₂ coproduction), compared to 20–30 GJ/ton in typical prior processes.

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Acknowledgement

We express gratitude to Prof. Joseph T. Hupp for his advice on mechanistic studies. We thank Peter E. Doan for the measurement and discussion on the EPR study. We acknowledge the contributions of Yanna Chen, Dongha Kim, Panagiotis Papangelakis, and Sungjin Park in XAS experiments. We also appreciate contributions in characterization and discussions by Selim Alayoglu and Zhu Chen. J.Y. gratefully acknowledges Prof. Robert J. Angelici for valuable discussions and suggestions. This work received financial support from Braskem America, Inc. J.Y. gratefully acknowledges support from the International Institute for Nanotechnology (IIN) Center for Nanocombinatorics Postdoctoral Fellowship and the Northwestern University International Institute for Nanotechnology. The authors acknowledge Carbon Minds database for providing the carbon intensity of EG and ethylene oxide. This research used resources of the APS, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Argonne National Laboratory, and was supported by the U.S. DOE under Contract no. DE-AC02-06CH11357, and the Canadian Light Source and its funding partners. This work made use of the EPIC, Keck-II, and SPID facility of Northwestern University’s NUANCE Center, which has received support from the ShyNE Resource (NSF ECCS-2025633), the IIN, and Northwestern’s MRSEC program (NSF DMR-2308691). The EPR studies were conducted in the laboratory of Prof. Brian M. Hoffman, supported by NSF grant CHE-2333907. C.M. and W.A.G. acknowledge support from the Liquid Sunlight Alliance, which is supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Fuels from Sunlight Hub under award number DE-SC0021266.

Supplemental Material

Additional discussion including the sample preparation for characterization and safety consideration; spectroscopic and microscopic characterizations of Ru-POM before and after eOOR; investigation of potential Ru-POM degradation; results of Ru-POM-mediated eOOR under different reaction conditions; scheme of paired HER-eOOR electrolyzer; process energy assessment; and eOOR performance comparison (PDF)

PDF file includes:
Supplementary Discussion
Supplementary Figs. 1 to 21
Supplementary Tables 1 to 4
References

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Resource type: Journal Article
Publisher: American Chemical Society
Published in: Journal of the American Chemical Society, 146(47), 32660–32669, ISSN: 0002-7863.
Languages: English