Redox-mediated electrosynthesis of ethylene oxide from CO2 and water

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.