Electrosynthesis of Ethylene Oxide from CO₂ and Water Only

Ethylene oxide (EO) is among the world’s most abundantly produced commodity chemicals due to its importance in the plastics industry, notably for manufacturing polyesters and polyethylene terephthalates (PET). The electrochemical production of EO from carbon dioxide (CO₂), water, and renewable electricity, can enable the consumption of 2 tons of CO₂ per ton of EO produced, in contrast to the emission of ~2 tons of CO₂ per ton of EO produced in existing thermochemical routes. This is achieved through an extended heterogeneous:homogeneous interface, using chloride as a redox mediator in conjunction with barium oxide-modified iridium oxide (BaO_x/IrO₂) catalysts. ^[1] ^[2] The catalysts enabled EO FEs of 85-91% and a selectivity of 98% in a current density range from 100 to 1500 mA/cm². When integrated into flow battery-analogue electrolyzer with an O₂/H₂O redox couple, we achieve record low energy input of 5.3 MJ/kg of EO, comparable to that of (emissions-intensive) existing industrial processes.<br/>[1] W.R. Leow, Y. Lum, A. Ozden, Y. Wang, D. Nam, B. Chen, J. Wicks, T. Zhuang, F. Li, E.H. Sargent* <i>Science</i> 2020, 368, 1228-1233.<br/>[2] Y. Li, A. Ozden, W.R. Leow, P. Ou, J.E. Huang, Y. Wang, K. Bertens, Y. Xu, Y. Liu, C. Roy, H. Jiang, D. Sinton, C. Li,* & E.H. Sargent* <i>Nat. Catal.</i> 2022, 5, 185-192.