The electrochemical production of ethylene oxide (EO) from CO2, water and renewable electricity could result in a net consumption of CO2. Unfortunately existing electrochemical CO2-to-EO conversions show impractical Faradaic efficiency (FE) and require a high energy input. Here we report a class of period-6-metal-oxide-modified iridium oxide catalysts that enable us to achieve improved CO2-to-EO conversion. Among barium, lanthanum, cerium and bismuth, we find that barium-oxide-loaded catalysts achieve an ethylene-to-EO FE of 90%. When we pair this with the oxygen reduction reaction at the cathode, we achieve an energy input of 5.3 MJ per kg of EO, comparable to that of existing (emissions-intensive) industrial processes. We have also devised a redox-mediated paired system that shows a 1.5-fold higher CO2-to-EO FE (35%) and uses a 1.2 V lower operating voltage than literature benchmark electrochemical systems.
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This work was supported by the National Research Council Materials for Clean Fuels program (MCF-109), the Ontario Ministry of Colleges and Universities (grant ORF-RE08-034) and the Natural Sciences and Engineering Research Council (NSERC) of Canada (grant RGPIN-2017-06477). We thank P. Karimi, X. Wang, Y. C. Li, J. P. Edwards and C. P. O’Brien for discussions. Y. Li acknowledges financial support from the China Scholarship Council (201906745001). W.R.L. acknowledges financial support from an A*STAR Young Individual Research Grant (grant number A2084c0180).
Y. Li, A.O., W.R.L, P.O. and E.H.S. have filed provisional patent application number 63/265.897 regarding the electrosynthesis of oxiranes. The other authors declare no competing interests.
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Li, Y., Ozden, A., Leow, W.R. et al. Redox-mediated electrosynthesis of ethylene oxide from CO2 and water. Nat Catal 5, 185–192 (2022). https://doi.org/10.1038/s41929-022-00749-8
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