Ethylene glycol (EG) is a commodity chemical, but its industrial production heavily relies on fossil-based feedstocks (that are, oil-based ethylene and coal-based syngas) and faces high carbon footprint. Herein, we report one-step electrosynthesis of EG from an important C1 platform molecule─methanol (MeOH), via oxidative C–C coupling at the anode. Over a boron-doped diamond (BDD) electrode, EG was produced with a Faradaic efficiency of 34.3% and a selectivity of 48.7% at a current density of 100 mA cm–2, delivering a productivity of 639 μmol cm–2 h–1. Mechanistic studies revealed that the reaction proceeded via a radical-mediated pathway, wherein H2O was first oxidized to the hydroxyl radical (•OH) on the BDD electrode, which mediated C–H bond activation of MeOH to deliver the •CH2OH intermediate, following C–C coupling to generate EG. To enhance EG selectivity, a paired-electrolysis strategy was designed that couples MeOH-to-EG at the anode and reduction of the byproduct formaldehyde to MeOH at the cathode. In a membrane-free flow cell, EG selectivity was increased from 48.7% to 72.1% with cycling stability over 80 h. This work demonstrates the opportunity to synthesize carbon-chain-propagated chemicals from basic C1 feedstock via radical-type C–C coupling by electrocatalysis.
Wang et al. (Sun,) studied this question.