Microenvironment regulation breaks the Faradaic efficiency-current density trade-off for electrocatalytic deuteration using D₂O

The high Faradaic efficiency (FE) of the electrocatalytic deuteration of organics with D₂O at a large current density is significant for deuterated electrosynthesis. However, the FE and current density are the two ends of a seesaw because of the severe D₂ evolution side reaction at nearly industrial current densities. Herein, we report a combined scenario of a nanotip-enhanced electric field and surfactant-modified interface microenvironment to enable the electrocatalytic deuteration of arylacetonitrile in D₂O with an 80% FE at −100 mA cm⁻². The increased concentration with low activation energy of arylacetonitrile due to the large electric field along the tips and the accelerated arylacetonitrile transfer and suppressed D₂ evolution by the surfactant-created deuterophobic microenvironment contribute to breaking the trade-off between a high FE and large current density. Furthermore, the application of our strategy in other deuteration reactions with improved Faradaic efficiencies at −100 mA cm⁻² rationalizes the design concept.