High-purity ethylene production via indirect carbon dioxide electrochemical reduction.

High-purity ethylene production from CO electroreduction (CORR) is a coveted, yet arduous feat because the product stream comprises a blend of unreacted CO, H and other off-target CO reduction products. Here we present an indirect reduction strategy for CO-to-ethylene conversion, one that employs 2-bromoethanol (Br-EO) as a mediator. Br-EO is initially generated from CORR and subsequently undergoes reduction to ethylene without the need for energy-intensive separation steps. The optimized AC-Ag/C catalyst with Cl incorporation reduces the energy barrier of the debromination step during Br-EO reduction, and accelerates the mass-transfer process, delivering a 4-fold decrease of the relaxation time constant. Resultantly, AC-Ag/C achieved a FE of over 95.0 ± 0.36% at a low potential of -0.08 V versus reversible hydrogen electrode (RHE) in an H-type cell with 0.5 M KCl electrolyte, alongside a near 100% selectivity within the range of -0.38 to -0.58 V versus RHE. Through this indirect strategy, the average ethylene purity within 6-hour electrolysis was 98.00 ± 1.45 wt%, at -0.48 V (vs RHE) from the neutralized electrolyte after CO reduction over the Cu/CuO catalyst in a flow-cell.