Microenvironment regulation of copper sites by chelating hydrophobic polymer for electrosynthesis of ethylene

Molecular catalysts can effectively steer the electrocatalytic acetylene semihydrogenation into ethylene, but realizing high Faradaic efficiency (FE) at industrial current densities remains a challenge. Herein, we report a ligand engineering strategy that utilizes polymeric N‑heterocyclic carbene (NHC) as a hydrophobic ligand to modulate the microenvironment of Cu sites. This polymeric NHC imparts appropriate hydrophobic properties for the chelated Cu sites, thereby moderating the H₂O transport and enabling easy access of acetylene. Consequently, the polymeric NHC chelated Cu exhibits an FE_ethylene of ∼97% at a current density of 500 mA/cm² in a flow cell. Particularly in a zero-gap reactor, the FE_ethylene consistently exceeds 86% across current densities from 100 mA/cm² to 400 mA/cm², reaching an optimal FE_ethylene of 98% at 200 mA/cm² and achieving durable operation for 155 h at 100 mA/cm². This work provides a promising paradigm to regulate the microenvironment of molecular catalysts for improving electrocatalytic performances under industrial current densities.