Iodide-bridged interfacial hydrogen bonds enable ampere-level electrosynthesis of deuterated acetic acid

Electrochemical dehalogenative deuteration in D₂O offers a sustainable and site-specific strategy for synthesizing deuterated molecules. However, this process is limited by restricted deuterium transfer in the interfacial hydrogen bond gap zone at the alkaline interface, resulting in a sluggish reaction rate. Here, an iodide-derived copper catalyst is designed to convert 2-monochloroacetic acid (MCAA) to acetic acid (AA), achieving a yield rate of 1.43 mmol h^-1 and lowering the potential by 200 mV compared with that of copper. Mechanistic studies reveal that, as hydrogen bond acceptors, iodide ions enhance the connectivity of interfacial water through I^-···H - O - H···O interactions, thereby facilitating deuterium shuttling and resulting in an Eley-Rideal deuteration mechanism. Moreover, the facilitated electron transfer and enhanced adsorption of MCAA induced by chemically adsorbed iodide ions contribute to the activation of MCAA. 19.8 g of AA-d₄ is obtained at 2.5 A within 40 h, highlighting the great promise of the iodide-modified strategy in catalyst and microenvironment design.