Electrocatalytic conversion of ethylene to ethylene oxide mediated by halide oxidation: Chloride vs. Bromide vs. Iodide

Ethylene oxide (EO) is among the most extensively used chemicals and is conventionally produced via the thermochemical oxidation of ethylene. This study demonstrates that a Pt-doped RuO2 and TiO2 composite (Pt-RuO2/TiO2) electrocatalyst drives ethylene oxidation to EO in the presence of reactive chlorine and bromine species in aqueous chloride and bromide solutions at Faradaic efficiencies (FEs) of ∼100 % and ∼90 %, respectively. Despite a lower FE, the bromine production is more feasible than the chlorine production and the as-formed bromine species remains stable for postreaction with ethylene. The iodine species exhibits a low reactivity toward ethylene. The activity of Pt-RuO2/TiO2 is substantially higher than that of other catalysts. Membraned and membraneless flow electrolyzers with a Pt-RuO2/TiO2 anode for ethylene oxidation and a Pt/C cathode for oxygen reduction are demonstrated at J = 500 mA cm−2. Technoeconomic analysis reveals reduction in the production cost of EO by 10 % with the membraneless electrolyzer.