Dual Redox Shuttles Drive Efficient Formamide Electrosynthesis

High electron transfer efficiency is critical for efficient electrocatalysis, and redox shuttles offer a promising strategy to enhance electron utilization for targeted products. Herein, we report the first work on dual redox shuttles operating simultaneously at the anode and cathode to promote electrosynthesis, as exemplified by the reaction of CH₃OH and NH₃ to produce formamide. The ionic liquid 1-ethyl-3-methylimidazolium triiodide (EmimI₃) in the electrolyte generates I₃^-/I^- and Emim⁺/Emim^• redox shuttles at the anode and cathode, respectively, which significantly enhanced reaction efficiency. A remarkable Faradaic efficiency of 76.1% toward formamide was achieved, along with a high production rate of 1087.2 μmol cm^-2 h^-1 in a single cell, far exceeding those reported in previous studies and control experiments without EmimI₃. Mechanistic studies revealed that the I₃^-/I^- shuttle promoted NH₃ oxidation to ^•NH₂ radicals, which then coupled with ^•CHO to form formamide. Meanwhile, the Emim⁺/Emim^• shuttle facilitated HCHO reduction to ^•CH₂O^-, which reacted with ^•NH₂ to further produce formamide. Thus, both electrodes synergistically drove the reaction, achieving a very high formamide yield. Moreover, this strategy facilitated NH₃ coupling with diverse substrates, including biomass- and plastic waste-derived polyols, leading to highly efficient formamide production and demonstrating broad applicability. Notably, the strategy is universally applicable to various electrodes.