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. Electrochemical dehalogenative deuteration in D2O is desirable but is hindered by restricted deuterium transfer. Here, the authors report an iodide microenvironment engineering strategy to rigidify the H bond network for the efficient dehalogenative deuteration of trichloroacetic acid to acetic acid.