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.
Wang et al. (Fri,) studied this question.